Forensic Evidence and the Police: the Effects of Scientific Evidence on Criminal Investigations

Forensic Evidence and the Police: The Effects of Scientific Evidence on Criminal Investigations

Joseph L. Peterson Steven Mihajlovic Michael Gilliland

October 1984

U.S. Department of Justice National Institute of Justice National Institute of Justice James K. Stewart Director

This project was supported by Grant Number 80-NI-AX- 0001, awarded to the Center for Research in Law and Jus- tice, University of Illinois at Chicago Circle, by the National Institute of Justice, U.S. Department of Justice, under the Omnibus Crime Control and Safe Streets Act of 1968, as amended. Points of view or opinions stated in this docu- ment are those of the authors and do not necessarily represent the official position or policies of the U.S. Depart- ment of Justice. FOREWORD

The precision of physical evidence and its presumed lack of bias and distortion compared to the testimony of witnesses has fascinated both the criminal justice community and the public, at least since Conan Doyle introduced us to Sherlock Holmes. Over the years, police have been urged by courts, blue-ribbon panels and the media* to adopt a more scientific approach to investigations and rely more on tangible clues than confessions of suspwts or eyewitness accmrnts.

The importance of crime laboratories has increasingly been recognized, particularly for the role they have played in a number of celebrated cases and in cases involving use of control led substances. Nevertheless, there has been little systemat ic verification that the collection of physical evidence such as fingerprints, blood and fiber and related trace evidence aids significantly in the investigation of crimes and the successful prosecution of the offender. In a world of shrinking budgets, law enforcement executives face tough decisions about allocating their limited resources. Without evaluation of the impact crime laboratories have on criminal investigations, resources may be allocated to other functions such as patrol +hat have evidenced clearer contributions.

In light of this situation, the National lnstitute of Justice is pleased to bring this report on the effects of scientific evidence on criminal investigations to the attention of law enforcement. The product of a 3- year study by researchers at the Center for Research in Law and Justice at the University of Il linois-Chicago Circle, the report indicates that scientific evidence can make a significant difference in criminal investigations. The information presented here sheds light on the effect of physical evidence collection and analysis on the investigation of various types of crimes, how clearance rates vary depending on whether physical evidence is collected, and the impact of physical evidence on the outcome of court cases. The report enhances the ability of law enforcement managers to make more informed decisions about the allocation of limited resources in both criminal investigations and crime laboratory operations.

1 would like to express the appreciation of the National lnstitute of Justice to police and crime laboratory executives of the cities of Peoria, Chicago, Kansas City and Oakland who opened their organizations to the scrutiny of the research. Their commitment to increasing our understanding of policing has given criminal justice managers objective information to guide policy decisions.

James K. Stewart Director ABSTRACT

The goals of this project are to describe the various uses of physical evidence in criminal investigationsand to assess the effects of scientificallyanalyzed evidence on the solution of serious crimes and the apprehensionand prosecutionof offenders. The absence of empiricalstudies in this area, coupled with the rapid growth of crime laboratoriesover the past decade,make this a particularlytimely and important research topic. Data have been coliectedfrom approximately2,700 case investigationsdrawn randomly from police and laboratoryfiles in four jurisdictions. Among the findings of the study are that rates of clearancefor robberiesand burglariesare significantlyhigher in investigations where physical evidence is examined,than in cases where it is not. Forensic evidencehas its greatest effect in cases which traditionally have the lowest solutionrates -- cases with suspectsneither in custody nor identifiedat the outset of the investigation. Moreover, a significantlyhigher percentageof persons arrested for the crimes of burglary and robbery are convictedin cases with forensic evidence. The effects of scientificevidence on the clearanceand prosecution of aggravatedassault cases is less pronouncedand, in many cases, not significantlydifferent from cases where forensicevidence is not used. A number of recommendations,aimed principallyat the patrol, detective,crime scene and crime laboratoryfunctions, are presented. These recommendations,plus suggestionsfor future research,have the goal of focusing limited police and scientific resourceson those investigationswhere physical evidence can make the greatest difference. TABLE OF CONTENTS

Abstract ...... iv Table of Contents ...... v . . Figures and Tables ...... Vll

Acknowledgments ...... Xi

ExecutiveSummary ...... XV

Chapter I: PROJECTBACKGROUND AND OVERVIEW ...... 1 Introduction ...... 1 Report Organization...... 4 Methodology ...... 6 StudySites ...... 12

Chapter 11: PHYSICALEVIDENCE AND THE INVESTIGATIONOF CRIMES: A BRIEF SUKMARY OF THE LITERATURE...... 23 Physical Evidence and Crime LaboratoryStudies ..... 23 Investigativestudies ...... 26 Judicial Outcon~eof Arrests ...... 32 Summary ...... 35

Chapter 111 : CWARACTERIZINGOFFENSES WHERE PHYSICAL EVIDENCE IS COLLECTEDAND EXAMINED ...... 37

Introduction ...... 37 The Criminal Offense and its Report to Police ..... 41 Taking the FreliminaryReport ...... 44 The Decisionto Investigate...... 50 Search of the Scene for Evidence ...... 55 Submissionof Physical Evidence: Proceduresand Purposes 58 CaseOutcome ...... 61 Summary ...... 66 Chapter IV: THE INVESTIGATIVEUSES OF PHYSICALEVIDENCE . . 65 Introduction ...... 69 Decisionto Examine the Evidence ...... 65 The Results of LaboratoryTesting ...... 79 Feedback and Value of ScientificResults to Users ... 89 Summary ...... 52 TABLE OF CONTENTS (continued)

Chapter V: PHYSICALEVIDENCE AND LABORATORYRESULTS .... 93 Introduction ...... Percentageof Crimes Reported to the PoliceWhich are Searched for PhysicalEvidence ...... IncidentVariables ~ssociated with the Number of Evidence

CategoriesCollected ...... ' a .*...... Categoriesof PhysicalEvidence Collected ...... Reasons for SubmittingEvidence for Analysis ...... Ratio of EvidenceExamined to EvidenceCollected .... LaboratoryResults ...... Value of Evidence. Resolvingthe Questionof Association LaboratoryResults Where Only Fingerprintsare Collected andExamined ...... Summary ...... a ......

Chapter VI: THE ROLE OF SCIENTIFICEVIDENCE IN THE CLEARANCE AND PROSECUTIONOF CRIMINALCASES ...... 133

Introduction ...... 133 The Evidenceand No-EvidenceSamples ...... 134 PhysicalEvidence and ClearanceRates ...... 135 Dispositionof Arrests ...... 149 Plea Bargainingand Charge Reduction ..*...... 158 Utility of FingerprintEvidence in Burglaries ..... 169 The Role of PhysicalEvidence in Drug Cases ...... 194 Homicides.Rapes and Arsons ...... 177 Summary ...... 185

Chapter VII: ESTIMATINGTHE EFFECTS OF PHYSICALEVIDENCE ON CLEARANCEAND CONVICTIONUSING LOG-LINEAR ANALYSIS ...... 189

Introduction ...... 189 The Effects of PhysicalEvidence on Clearance ..... 191 The Effects of PhysicalEvidence on Conviction ..... 280 Summary ...... 210

Chapter VIII: CONCLUSIONS.POLICY RECOMMENDliTLONSAND FUTURE RESEARCH ...... 211

Conclusionsand Recommendations ...... 211 Future Research ...... 229

References ...... 231 We are indebted to many persons who provided assistanceto us over the two and one-half years of this research project.

Our initial thanks must go to the police departments,crime laboratories and prosecutor'soffices in each of the participatingresearch sites: Peoria, Illinois;Chicago, Illinois;Kansas City, Missouri;and

Oakland,California. Without the assistanceand cooperationof many individualsin these locationsthis study would not have been possible.

In Peoria,we extend special thanks to Chief Allen Andrews of the

Peoria Police Departmentfor granting us permissionto gather information from his departmentand for attendingseveral meetings of our project advisory committee, Thanks, too, to CaptainWilliam Helm,

CaptainRobert Latham and Mr. Gregory Hochstetterwho helped in gaining access to various personnel,records and departmentalinformation. We are most grateful to Sergeant Peter Gerontes and the members of the crime scene unit, Sergeant Gerontes,his officers and Ms. Jan Dur- flinger,his administrativeassistant, were particularlyhelpful to us.

We would also like to thank the past and present State's Attorneys in

Peoria County,Mr. Michael Mihm and Mr. John Barra, and their First

Assistant,Hr. Robert Gaubas, for permittingus access to prosecutorand convictionrecords.

In the Bureau of ScientificServices Regional Laboratoryin Morton,

Illinois,we received completecooperation from Mr. Joseph Bubonic and his scientificand clerical staffs, Our sincere thanks to them. In the City of Chicago,we express our gratitude to Superintendent

Richard Brzeczek and the members of the ChicagoPolice Departmentfor their cooperation. Deputy SuperintendentsMatthew Rodriguezand Thomas

Lyons provided specizl help in facilitatingour work with the scientific and in-~estigationsservices divisionsof the agency. In particular though, we are indebtedto Mr. Marshall Considine,Director of the Crime

Laboratory,and the heads of the various laboratorysections: Robert

Boese, Naureen Casey,Bernadette Kwak, Arthur Paholke and Donald Smith.

Thanks,also, to Captain Renaldo Cozzi of the Records Divisionand

LieutenantHoward Finn for their help in accessingdepartmental records*

Lastly, we extend our thanks to Mr. Morgan Finley,Clerk of the Cook

County Court and his staff for help in searchingcourt records,

In Kansas City, we would like to thank Chief Norman Garon of the

Kansas City Police Departmentand his entire staff, In particular,we thank Colonel James Keiter, Colonel Joseph Smith, Major William Moulder and CaptainRobert Livingstonfor coordinatingour data gathering efforts, Our sincere gratitudealso goes to Mr. Gary Howell, director of the crime laboratory,and his scientificand administrativestaff, We are grateful,as well, to Mr. Albert Riederer,Jackson County District

Attorney,his Chief Trial Attorney,Mr. Robert Dakopolis,and Special

InvestigatorKevin Pose for their help in collectingcourt disposition data.

In Oakland,we extend our thanks to Chief George Wart, Deputy Chief

John Ream, and Captain James Stewart for their approval and support of the project, Ms. Jan Bashinski,director of the crime laboratory,and her scientificand clerical staff assisted our project in every way possible, We are grateful,also, to LieutenantMilton Evanson for his

xii FIGURES AND TABLES

Table 1-1. Total Crimes in Physical Evidence Sample ... 10

Table 1-2, Total Crimes in Non-PhysicalEvidence Sample 11

Figure 111-1. Physical Evidence Flow Chart ...... 40

Table 111-1, Top Five CategoriesCollected by Crime Type , . 57

Table 312-2. Crimes Reported to the Police and Percent Cl.eared (1979) ...... 63

Table IV-1. Chicago Crime Laboratory: Percentageof Physical EvidenceCases Submitted to the LaboratoryWhich are Examined ...... 72

Table IV-2, Kansas City Crime Laboratory: Percentageof Physical EvidenceCases Submittedto the LaboratoryWhich are Examined ...... 73

Table IV-3. Oakland Crime Laboratory: Percentageof Physical Evidence Cases Submitted to the LaboratoryWhich are Examined ...... 75

Table V-1. Percentageof Crimes Reported to the Police Which Received a Crime Scene Search by an Evidence Technician ...... 95

Table V-2. IncidentVariables Which Have a PositiveAsso- ciation with the Number of EvidenceCategories Collected ...... 96

Table V-3. Kansas City Crimes Against Persons: Extent of Injury by Number of PhysicalEvidence CategoriesCollected ...... 99

Table V-4. Kansas City: Crimes Against PersonsNumber of Physical Evidence CategoriesCollected by CollectingAgent ...... 104

'Table V-5. Percentageof the Time Various Police Personnel are CollectingAgents in Cases in Which Four or More Categoriesof Evidence are Collected ... 105

Table V-6, Reasons for Submissionof Evidence ...... 108

Table V-7. Percent of Physical EvidenceCategories CollectedWhich are Examined by Crime Type . . 112

Table V-8. Results Derived From the LaboratoryExamination of PhysicalEvidence ...... 114

vii FIGURESAND TABLES (continued)

Table V-9, Peoria: LaboratoryResults by EvidenceCategory and Crime Classification ...... 118

Table V-10. Chicago: LaboratoryResults by Evidence Categoryand Crime Classification ...... 119

Table V-ll. Kansas City: LaboratoryResults by Evidence Categoryand Crime Classification ...... 120

Table V-12. Oakland: LaboratoryResults by Evidence Categoryand Crime Classification ...... 121

Table V-13. Percent of Time LaboratoryResults Are Success- ful in Determiningif Persons/ObjectsAre Associatedwith one Another ...... 124

Table V-14, Utilizationof FingerprintEvidence ...... 127 Table V-15, Results of FingerprintAnalyses ...... 129

Table VI-1. Total Four City Evidenceand No-Evidence Samples ...... 136

Figure VI-1, ClearanceRates for Evidenceand No-Evidence Cases ...... 137

ClearanceRates for Evidenceand No-Evidence Cases ...... 138

Table VX-3. Police Knowledgeof Suspectsat Outset of Investigation ...... 141

Table VI-4. Time Elapsed From Discoveryof Crime to Report to ~olice/PoliceResponse ...... 143

Table VI-5. Witness InformationProvided to Police at Outset of Investigation ...... 145

Table VI-6. ClearanceRates Controllingfor Police Knowledge of Suspectsat Outset of Investigation .... 147

TableVI-7, ClearanceRates Controllingfor Time Elapsed from Crime Discoveryto Report to/Responseby thePolice ...... 148

Table VT-8. ClearanceRates Controllingfor Witness Infor- mation Providedto Police at Outset of Investi- gation ...... 150

Table VI-9. Percent of Arrests Leading to Formal Charges Being Filed for Evidenceand No-EvidenceCases. 152

viii FIGURESAND TABLES (continued)

Table VI-10. Percent of Arrests Leading to Convictionsfor Evidence and No-EvidenceCases ......

Figure VI-2. Percent of IncidentsResulting in At Least one Conviction ......

Table VI-11. Percent of IncidentsResulting in at Least one Conviction ......

Figure VI-3. Judicial Outcome of Cases Where ProsecutorFiled Charges (Defendant~ased) ......

Figure VI-4. Percent of Convictionsin Which the Arrest Charge Was Downgraded ......

Figure VI-5. Peoria: Results of LaboratoryTesting by Type of Judicial Disposition ......

Figure VI-6. Chicago: Results of LaboratoryTesting by Type sf Judicial Disposition ......

Figure VI-7. Kansas City: Results of LaboratoryTesting by Type of Judicial Disposition ......

Figure VI-8. Oakland: Results of LaboratoryTesting by Type of Judicial Disposition ......

Table VI-12. Case Outcome Statisticsfor ~urglary/Property Crimes Controllingfor Fingerprintsand Other Evidence ......

Table VI-13. DescriptiveStatistics for Evidence,No-Evidence and FingerprintOnly Cases ......

Table VI-14. Drug Cases: DescriptiveStatistics ......

Table VI-15. ConvictionRates for Drug Cases With Laboratory identification ......

Table VI-16. Outcome of HomicideCases in Which Physical Evidence Is Analyzed ......

Table VI-17. Outcome of itape/Sex-RelatedOffenses in Which Physical Evidence Is Analyzed ......

Table VI-18. Outcome of Arson Offenses in Which Physical Evidence Is Analyzed ...... FIGURESAND TABLES (continued)

Table VI-19. Rates of Convictionfor Persons Arrested for Murder, Controllingfor LaboratoryResults . .

Table VI-20. Rates of Convictionfor Persons Arrested for Rape, Controllingfor LaboratoryResults ...

Table VII-1. Variables for Log-LinearAnalysis Using Clearanceas the Dependent Variable ......

Table VII-2. AdditiveEffects of Variables E T W 0 on Clearance ......

Table VII-3. EstimatedEffect of Evidence on Odds for Clearancefor Model M(1) ......

Table VII-4. Variables for Log-LinearAnalysis Using Convictionas The DependentVariable .....

Table VII-5. AdditiveEffects of Variables E R T 0 on Conviction ......

Table VII-6. EstimatedEffect on Odds for Convictionof Evidence With No ComonOrigin over No Evidence i~odel~(2)) ......

Table VII-7. EstimatedEffect on Odds for Convictionsf EvidenceWith Common Origin over No Evidence {Model ~(2)1 ......

Table VII-8. EstimatedEffect on Odds for Convictionof Evidence With Common Origin over Evidencewith No Common Origin {Model ~(2)) ......

Table VII-9, EstimatedEffect on Odds for Convictionof Evidence With No Common Origin over No Evidence {Model ~(3)1 ......

Table VII-10. EstimatedEffect on Odds for Convictionof EvidenceWith Common Origin over No Evidence {Model ~(3)1 ......

Table VII-11. EstimatedEffect on Odds for Convictionof Evidence With Common Origin over Evidence with No Common Origin {Model ~(3)) ...... help in coordinatingour data gatherers'review of police department records.

We wish to express our appreciationto the members of our project advisorycommittee for their support and counsel throughoutthe study period. These individualskept the project on course and provided invaluableassistance by commentingon data collectionstrategies, preliminaryanalyses of the data, and draft versions of the final report. The members of the advisory committeeare: Mr. Jerry Chisum,

Manager of the Modesto, CA Regional Crime Laboratory;Professor Oliver

Schroeder,Case Western Reserve University;Professor Wesley Skogan,

NorthwesternUniversity; Mr. Todd Taylor,Hallcrest Systems, Inc.; and

Mr. Anthony Yazback,private consultant.

Mr. William Saulsburyserved as our National Instituteof Justice grant monitor during the project and did his usual professionaljob,

Bill distinguisheshimself by his calm, steady and thoughtfulapproach to matters of grant administration. Mr. Kenneth Field of the Forensic

Sciences Foundationprovided assistance,especially in readingdrafts of earlier chaptersand offering some much needed criticism.

Our field data collectorsdid a fine job in the various study sites. They include: Ms. Debra Van der Wal, Ms. Carole Schmitt,Ms.

Rose Laird, Ms. Joanne Kron and Mr. John Bashinski. Dr. Dennis Gil-

Piland,Professor of Statisticsand Probabilityat Michigan State Uni- versity provided special assistancein engineeringthe log linear analysis and the writing of Chapter VII of the report. Ms. Francis Kozuch applied her editorialtalents to the final manuscriptand her efforts are much appreciated.

xiii Lastly, I would like to thank the staff and associatesof the

Center for Research in Law and Justice who labored long and hard on this project. We particularlywant to thank our cierical and student research staff members: Ms. Carol Gielarowski,Mrs. Theresa Johnson-

McKelphin,Ms. F. DesireeBoyd, Ms. Bobbie Dunbar,Ms, Yvonne Smith and

Ms. Mary Pallen. These staff members are responsiblefor the entry and cleaning of the project data and the typing of all interim and final manuscripts. They have all exhibitedthe greatest patience and dedica- tion that any project director could ever want. We, also, thank Doug

Thomson,Wayne Kerstetter,Fred DuBow, Joe Nicol, Jim Osterburg,Herb

Hamiltonand Dick Ward for reading drafts of chapters and offering their criticismsand suggestions.

The authors,of course,assume total responsibilityfor all deficienciesand shortcomingsof this report.

xiv EXECUTIVESUMMARY

Backeround

The goals of this project are to describe the various uses of physical evidence in criminal investigationsand to assess the effects of this scientificallyanalyzed evidence on the solution of crimes and the apprehensionand prosecutionof offenders, The absence of empirical studies on this topic, coupled with the rapid growth of crime laboratories over the past decade,make this a particularlytimely and important research topic,

Prior research into this area has not adequatelypinpointed the uses and effects of evidence for various reasons. Because physical evidence is examined in a small percentageof crimes investigatedby the police,past studies have lacked the necessary statisticalbasis to form reliable conclusions. Researchershave also been faced with record keeping systems inadequateto permit measurementof the impact of scientific evidence. Another problem repeatedlyseen is the assumptionthat fingerprintsare the only form of evidence registeringan impact on cases. Finally,prior research tends not to differentiatelaboratory analyzed evidence from other types of tangible evidence that may be collected in an investigation.

Although the present project certainlydoes not answer all the unresolvedquestions about the value of physical evidence,it does provide new insights into the patterns found in the recovery of evidence from major crimes. This study also delineatesthe types of evidence routinelyrouted to the laboratoryfor analysis and records the success of laboratoriesin answeringthe questionsposed by investigators. Most important of all, this study documentsthe effects of the evidence on the outcome of cases. The central questionsexplored in the study are as follows:

o What categoriesof physical evidence are collectedfrom the scenes of major crimes and which types are most successfulin linking offenderswith these offenses?

o Does the collectionand examinationof physical evidencehave an appreciableeffect on the clearancesof criminal investigations?

o How does the value of physical evidence compare with other types of information or strategiesemployed by detectivesin investigatingcrimes?

s What effect does physical evidencehave on the quality of arrests,expressed in terms of the fraction of arrests which lead to conviction?

o To what extent does the utility of physical evidencevary from one jurisdictionto another?

o May guidelinesbe developedto assist crime scene technicians,detectives and criminalists in determiningin which types of offenses physical evidence is most likely to have the greatest payoff?

Major Findings

The rates of clearancefor robberiesand burglaries:are significantly higher in investigationswhen physical evidence is collectedand examined than in cases when it is not. Forensic evidencehas its greatest effect in cases which, traditionally,have the lowest solution rates--caseswith suspectsneither in custody nor identifiedat the preliminaryinvestigation stage. Koreover,significantly more persons arrested for the crimes of burglary and robbery are convicted in cases with analyzed forensic evidence. Rape prosecutionsalso result in higher rates of convictionwhen semen is identifiedor when other physical evidence links the defendantwith the victim. Convictionrates, in two of the jurisdictionsstudied, are significantlyhigher in homicide cases where physical evidence linking the offenderwith the crime is developed. The effect of evidence on the clearanceand prosecutionof aggravatedassault cases is less pronounced and, in many situations,not significantlydifferent from cases where scientificevidence is not used.

Approach

Approximately1,600 investigationshave been reviewed in which physical evidencewas collectedand examined and 1,100 cases where physical evidencewas not used. Em~iricaldata were collected in four jurisdictions: Peoria,Illinois; Chicago, Illinois; Kansas City, Mis- souri; and Oakland,California. These jurisdictionshave been selected on the basis of size and geographicaldistribution, their different approachesto evidence retrievaland analysis,and their interest in exploring the researchquestions posed at the beginning of the project.

The data have been collectedfrom case files maintainedby the respectivepolice agencies,crime Laboratories,prosecutor and court offices in the differentjurisdictions. Data collectionfocuses on the

xvii five principal investigativestages of serious crimes: the crime

report, the preliminaryinvestigation, the follow-up investigation,the

collectionand analysis of physical evidence,and the judicial outcome

of the case. The physical evidencecases in the study have been selec-

ted randomly from crime laboratoryfiles, primarily from the offense

categoriesof homicide,rape, aggravatedassault, robbery, and burglary.

The cases in the sample without physical evidencehave been selected

randomly from cases lacking physical evidence in the police files.

These no evidence cases are confined to the crime categoriessf robbery,

aggravatedassault and burglarybecause of the high incidenceof physi-

cal evidence collectedin the categoriesof homicide and rape. This sampling approach is used to attempt to isolate the effects of the scientificevidence alone on the results of these cases,

Following the introductorychapter and a brief summary of the literatureon physical evidence and criminal investigations,Chapter I11 introducesthe discussionof research results by first describingthe process which controls the recognition,collection and examinationof physical evidence in the crime laboratory, In addition,descriptive informationabout the 1,600 physical evidence cases in the sample is presentedand interjurisdictionaldifferences noted, The model de- scribedbegins with the commissionof the crime, its report to the police and on through the preliminaryand follow-up stages of the investigation. The followingincident variables subsequentlyare shown to affect the gathering of physical evidence: the time lapse between the discoveryof the crime and its report to police; the extent of physical

Interactionbetween the offenderand the scene or victim; the type of locationwhere the crime occurred;the presence of witnessesand the identityand whereaboutsof suspects. One of the most significant characteristicsof these investigationsinvolving physical evidence is the high percentageof cases in which a suspect is in custody at tile time the search for evidence takes place. Approximatelyone-half of the crimes in the Peoria and Oakland samples,one-third of the cases in

Chicagoand one-fifth of the cases in Kansas City have suspects in custody,

Blood, hair, firearms and fingerprintsare the forms of physical evidencemost frequentlycollected and examined in the laboratory,

Suspectedsemen is high on the list of physical evidence collectedin sexual assault cases. Evidence submittedto the laboratoryin burglary and property crimes usually falls into one of the trace evidence or toolmark categoriesin additionto fingerprints. Evidence technicians and police officers specializingin crime scene processingare the principal collectorsof this evidence.

Host evidence is submitted to the laboratoryfor the purpose of establishingan associationamong offenders,victims, crime scenes,and instruments(weapons, tools). The primary objectiveof evidence submissions in rapes and arsons is to identify traces of suspectedsemen and volatile liquids,thereby helping to establishan element of the crime,

Evidence is also submittedfor the purpose of corroboratingor refuting other informationgathered by investigatorsfrom victims,witnesses and

xix suspects. Evidence often helps reconstructhow a crime actually occurred.

The chapter concludeswith a review of overall rates of clearance, chargingand convictionof offenders in physical evidence cases. Very high rates of clearanceare found,ranging from 84% of the cases in

Oakland to 49% of the cases reviewed in Kansas City. High rates of chargingand convictionof defendantsare also the rule, There is a strong indicationat this early stage of review and analysis that physical evidence cases are quite special,if for no other reason than their success in survivingthe numerous screeninglevels of the criminal justice system, The remainderof the report attempts to explain the seasons for this success.

Investi&ive Uses of Physical Evidence

Chapter IV focuses on investigativeuses of physical evidence by first reviewingthe fractionof evidence collected from the field which is actually examined scientificallyand various priority systems used by laboratoriesin decidingwhich cases will receive attention first. The nature of the crime, its seriousness,the perishabilityof the evidence, and the presence of suspects are the primary factors taken into consideration.

Several examplesdrawn from the files of the participatingcrime laboratoriesare included to illustratethe results of laboratorytesting of evidence and its value to these investigations. The results range from cases in which materials are simply identifiedor classified to those in which conclusivelinkages are establishedbetween a suspect and the crime. Included,also, is an illustrationof physical evidence which helped to exculpatea rape suspect.

This chapter concludeswith a discussionof the manner and speed with which results are conveyed to investigators.

LaboratoryResults

Chapter V describes those characteristicsof criminal incidents which help to explain the types and quantitiesof physical evidence collected. It summarizesstatistically the primary reasons evidence is submittedto the laboratoryand the percentageof time evidence is successfulin associatingor disassociatingthe offenderwith the crime scene and/or victim. The chapter concludeswith a discussionof sample cases in which fingerprintsare the only form of evidence collectedand examined.

More violent personal crimes resuit in greater quantitiesof evidence being gathered than less serious offenses. In personal crimes, more evidence is gathered at the preliminaryinvestigation when detectives have the poorest informationabout suspects. However,in property offenses,more evidence is gathered when suspects are in custody or immediatelyidentified. Only a fraction of the evidence collectedfrom the field is actuallyexamined. A higher ratio of evidence collectedin property crimes is examined than in personal crimes.

The percentageof laboratoryresults leading to a statementof common origin (a match between two items of evidence) is highest in personal crimes. On the other hand, physical evidence collectedin property crimes is more likely to result in showing items of evidence

xxi have a differentorigin, Peoria has the greatest success in determining

the origin of firearms evidence,toolmarks, fingerprints, and trace

evidence, Oakland determinesthe origin of bloodstainsand hair evidence most frequently. Chicago and Kansas City have the greatest suc-

cess in identifyingthe presence of semen submittedin sexual assault

cases.

In personal crimes, firearmsand fingerprintsare the evidence categorieswhich resolve the question of associationmost often, Blood- stains, on the other hand, have the poorest record for associating persons and locationsin three of the four cities. Trace evidence

(paint, glass and fibers) and toolmarks lead to the greatest success in resolvingthe question of associationin property crimes. Fingerprints, in contrast to their usefulnessin personal crimes,are much less effective in associatingsuspects and crimescenes in property crimes,

The Role of ScientificEvidence in the Clearance and Prosecutionof Criminal Cases

Chapter VIfocuses on the rates of clearance,charging and conviction of cases in which physical evidence is collectedand examined versus the sample of cases In which no physical evidence is gathered.

Because the no evidence sample is, of necessity,restricted to the crime categoriesof robbery,aggravated assault and burglary/propertycrimes, only cases with physical evidence from these same crime categoriesare included in this analysis,

Examinationof the cases reveals significantdifferences in the rates of clearance,charging, conviction, plea bargainingand charge reduction. The differences are most pronouncedin the crime categories

xxii of robbery and burglary. The rates of clearancefor the cases with physical evidence are significantlyhigher in most cities while controllingfor the presence of suspects,witnesses and speed with which crimes are reported to, or respondedto, by the police.

At the court level, cases with forensic evidence result in significantly higher rates of convictionthan cases without this evidence. The cases with physical evidence tend to go to trial a higher percentageof

the time; also, the physical evidence cases in which the laboratory reaches a common origin conclusionare more likely to be adjudicatedat

trial, Rates of dismissalare higher when the laboratoryresults either disassociateor fail to associatethe defendantwith the crime.

Although it is not possible to compare the dispositionsof hom-

icides, repes and arsons using this evidencein0evidence dichotomy,it

is possible to look at their court dispositionswhile controllingfor

laboratoryresults, In the offense category of homicide,rates of

convictionare higher in cases with common origin laboratoryresults in

two jurisdictions(Kansas City and Oakland). In rape cases, the rates

of convictionare higher in all jurisdictionswhen semen is identified

or other evidence linking the suspect with the victim is found. But the

differencesare statisticallysignificant only in Chicago and Oakland.

Estimatingthe Effects of Physical Evidence on Clearance and ConvictionUsing Log-LinearAnalysis

The marginal effects of physical evidence on clearanceand convic-

tion were investigatedin Chapter VXwhile controllingfor the effects

of other factors,such as the identityof a suspect,presence of witnes-

ses or citiz.enreport/police response time. Typically,analyses are made by calculatingthe clearanceor convictionrate for cases with and without physical evidencewith the control variablesat specified levels. The question arises as to whether the lack of control for these other explanatoryvariables at the same time may cause the results to be misleading.

Chapter VII reports on the results of a more sophisticatedanalysis to quantify and model the simultaneous,joint effects of physical evidence and several other independentvariables on selecteddependent variables. Three models are presentedwhich describe the effects of scientificevidence on clearanceand conviction. The advantageof this approach is that the interactionsand differentialeffects of physical evidence on the dependentvariables (clearanceand conviction)can be estimatedthat might otherwisego undetected.

The results show that the effects of physical evidence on clearance and convictiocdepends upon the jurisdictionbeing discussedand the class of offense in which the evidence is examined. Generally,evidence has its greatest impact on clearanceof robberiesand burglariesin the jurisdictionsof Peoria and Oakland. Moreover,the effects of physical evidence depends upon the presence or absence of witnessesand suspects at the time the preliminaryinvestigation is initiated. Scientific evidencehas its greatest effect on clearancewhen suspects are not in custody or named and placed at the outset of the investigation. On the other hand, physical evidencehas a higher associationwith clearance when witnesses are present. In assault cases physical evidencehas its highest associationwith clearancewhen suspects and witnesses are availableat the time of the crime report.

xxiv The presence of physical evidence is associatedwith the greatest increasein odds for convictionin Kansas City, followed by Oakland,

Peoria and Chicago. As in the previous examinationcf clearanceodds, the analysis shows that it is necessary to control for both offense categoryand jurisdictionin estimatingthe effects of evidence on conviction. Evidence generallyhas its greatest effect on robberiesand burglaries,but with a negligibleeffect on assaults (except for Kansas

City). Upon contrastingthe effects of common origin laboratoryresults with all other forms of laboratoryresults, it is found that only in the category of burglary do these more specific laboratoryfindings have an observableeffect on increasingthe odds for conviction.

Conclusions,Recommendations and Future Research

The final chapter of the report offers a number of policy rec- ommendationsfor police agencies and crime laboratoriesand suggests pcssible directionsfor future research.

Policies for Improvingthe Use of Physical Evidence

These policy recommendationsare based on the findings of the current researchand fall into six primary areas:

Patrol Operations- Patrol units must not only fulfill their tradi- tional responsibilitiesof evidence recognitionand crime scene preservation, but must also followmore explicit and systematicguidelines as

xxv to when evidence techniciansare to be called to the scenes of crimes and their responsibilitiesonce techniciansarrive.

- Technicianunits should be placed in the same organizationalunit as the crime laboratory. In addition,technicians' crime scene and investigativeroles and responsibilitiesshould be expanded and their incidentaltechnicai and evidence courier activities reduced.

Criminal - Investigatorsshould adopt more rational guidelines,including consideration of potential physical evidence,in deciding if to investigatecrimes. Investigatorsshould recognizethe value of physical evidence in making arrests which have a greater probabilityfor resulting in convictions. Detectives,also, must work more closely with crime laboratoriesin assigningpriorities to cases submittedfor analysis,

Crime Laboratory- Laboratoriesmust take a more active role in developingpolicies guiding the investigationof crime scenes and the setting of prioritiesfor the examinationof cases in the laboratory.

Laboratorymanagers must not allow the demand for examininghigh volume evidence categoriesto consume an inordinateportion of scientific resources,at the expense of eases where more detailed and time- consuminganalyses are required. Laboratoriesmust also adopt management reportingsystems to permit an ongoing assessmentof the impact of physical evidence on case investigationsand prosecutions. Prosecution- Prosecutorsshould provide feedback to laboratories on the dispositionsof all cases involvingphysical evidence. In order to improve communicationsone suggestionoffered is to designatea forensic science resourceperson in {he prosecutor'soffice who can coordinateinquiries, investigations and overall liaisonwith the laboratory.

Police Administration- The top level administrationof the parent law enforcementagency should develop greater awarenessand sensitivity to the needs of their crime scene search and laboratoryoperations.

They must also see to it that well-definedand realisticpolicies are formulatedand followed,to guide the search for, collection,and examination of physical evidence. They should also support the conduct of research in their laboratoriesand investigationupits to assess the impact of physical evidence.

Future Research

Additionalresearch is needed in the forensicscience - criminal investigationarea to develop more detailed evaluationsof scientific services and their role in the investigationsf rases, A prerequisite for engaging in future research,though, is a laboratory-basedcase managementreporting system. Such a system would permit laboratoriesto trace the flow and outcomes of eases in which physical evidence is examined, Only with such a system can laboratoriesbegin to collect,in a cost-effectivefashion, the necessarydata for defining the contribution of evidence categoriesto the investigationof different crime categories.

xxvii With a managementreporting system in place, two basic types of research are recommended: one quasi-experimentaland the other experimental. The quasi-experimentalstudies would entail making improvements or intensifyingevidence utilization efforts in a particularcrime categoryor, perhaps, a geographicalarea of a city. The purpose would be to measure the differencesin the rates of clearance,arrest, charging and convictionof cases. The experimentaldesign would require that cases reported to the police be randomly assigned to experimentaland control groups. The experimentalcases would receive intensivecrime scene search and evidence evaluationwhile the control cases would either not be examinedat all, or receive only routine processing. Such a design would permit researchersto isolate the effects of the physical evidence and laboratoryanalysis on the cases in-questionin a far more controlledand rigorous fashion than either the quasi-experimental design or the archival,case records approach used in this study.

xxviii

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207) 207)

V—4 V—4

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—104— —104—

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EVIDENCE EVIDENCE

TABLE TABLE

KANSAS KANSAS

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I I

I a

I 0% 2% (N=48) 17% Prop. in 31% 27% 25% categories Oakland 8% 6% (N=332) 16% 13% Pers. 35% 42% of included 7% 9% (N=161) 12% Prop. 16% 29% cases 47% number City the LABORATORY EVIDENCE Pers. Kan 7% 3% total (N=431) 41% 14% 29% of 20% THE the Jurisdiction V—8 Prop. to 5% 2% 2% (N=123) FROM 11% PHYSICAL 49% 38% —114- OF Chicago laboratory TABLE Pers. refers 1% 5% (N4l1) 10% 21% 58% the 20% DERIVED by table Prop. 2% 0% (N=97) 12% 20% 54% 20% EXAMINATION RESULTS Peoria this Pers. in analyzed 5% 5% 6% (N=421) 36% 44% sample. 24% ID. value study N fyi evidence I the of The Result fferent Ident Laboratory Classify Inconclusive Common Origin Origin Negative Di Reconstruct of and and two two the the upon upon and and in in as as and and common origin origin her her of of the the the of of In the the be be suspec suspec two two of of of of origin origin Chicago to presence presence property property the the source, source, twice twice origin. origin. 5 conclusively conclusively common factor factor category category Forty—four Forty—four the the percent percent sugar. sugar. example example a comparable comparable or or suspected suspected the the common and and substances, substances, these these thought thought by by about about of of substances For For in in crime crime category. category. are are common percentage milk milk another another in in the the example, example, cities. cities. detect detect be be was was has has “identify/classify” “identify/classify” in in crimes crimes are are to to than than probably probably from from it it cases, cases, fifty—four fifty—four under under packet packet lowest lowest sizes sizes origin origin the the above above other other Oakland Oakland controlled controlled a would of of property property contamination/deterioration and and more more the the Oakland Oakland Peoria Peoria the the the the and and or or unable unable both both the the personal personal time time here here grouped grouped sample sample in in common (in (in but classified classified be be substance substance possibly, possibly, in in number number with with crimes crimes from from liquids, liquids, identifications. identifications. City the the the the the the from categorized categorized —115— nothing been been the the forms forms may cases cases of of noted. noted. of of quantity quantity be be which origin), origin), are are be be has has cities cities of of results cases cases note results results results, results, results results to to Kansas Kansas are are are are greatest to to of of results results personal personal negative negative the the two flammable flammable small that that out out evidence evidence common the the in in results results not not the the should should laboratory laboratory a origin origin the the origin origin standard standard the the percentage percentage than than crimes. crimes. crimes crimes of of results results notes notes of of category category a blood blood the the to to One fluid, fluid, turns examination examination have have row row primary primary process process results results 2l 2l percentage percentage small small common common often often due due with with with with the the crime crime A City. City. origin” origin” determined determined The The of of the the of of property property property property seminal seminal with is is example, example, second second percentage percentage more more in in lowest lowest in from from comparisons; comparisons; of of possibly possibly results results sample. sample. be be situations, situations, evidence evidence for for The The Kansas Kansas The The compared compared the the personal personal to to substance “common the the statement statement link link category, category, the origin results results offense of of category results does the the other other percentage ted ted oin, percent percent evidence evidence Results Results has submission. submission. the the then then bloodstains.

samples samples

a a

U U

1 1

B B

I I

U U U

B B

I I I I to three. Peoria and Oakland generally reserve their property crime examinations for cases in which both evidence and standards are sup plied, while Kansas City and Chicago examine cases lacking standards

where scientific results may aid in deciphering how a crime was commit

ted, but would not lead to a common origin conclusion.

The Oakland laboratory has the highest percentage of laboratory

reports which conclude that two items of evidence do not have a common

origin. It appears the policy in Oakland is for their examiners to be

much more explicit in their laboratory reports about the failure of two

items to match with one another and, thereby, indicate they do not share

a common source. There is a tendency in the other laboratories to de clare inconclusive results in such cases. The low percentage of dif

ferent origin results in a city such as Chicago is also a reflection of

the smaller percentage of cases submitted with known “standards.” Different origin results constitute valuable information, for they

may demonstrate to investigators that they are pursuing the wrong

suspect or are operating under a faulty hypothesis as to how the crime occurred.Evidence submitted in property crimes is more likely to result

in a different origin result than that submitted in personal crimes.

The reconstruction category basically includes examinations which

may assist in determining how a crime was or was not committed. These are commonly cases where evidence alone is submitted for examination with an accompanying inquiry; “Does the evidence indicate a crime occur

red?” or “Was it committed in this way?” Informing investigators that a

lock was or was not picked would be an example of reconstructive inform ation aiding an investigation.

Inconclusive results occur when laboratory findings fail to yield an informative statement or conclusion.

—116—

in in

rate

with with

the

and

rate

with

(N12), (N12),

common common

Kansas

testing

evidence evidence

develop

Kansas Kansas

a a

The The

6% 6%

when when

city, city,

results results

and and

highest highest

other

of of

to to

this this

small small

categories

personal personal

have

offender offender

only only

correspond correspond

the the

is is results

the the

low low

Peoria, Peoria,

in in

an an

conclusion conclusion

city city

conclusion conclusion

Peoria Peoria

crimes.

a a

laboratory laboratory

evidence evidence

in in

which which

a a

has has

identifications identifications

a a

given given

in in

of of

in in

percent percent

in in

evidence evidence

values values

from from

in in

origin origin

links links

Oakland Oakland

mark mark

are are

also also

crimes crimes

submitted submitted

in in

cases cases

some some

firearms firearms

70% 70%

The The

positive positive

is is

blood blood

Oakland Oakland

results results

crimes crimes

of of

Common Common

sex—related sex—related

results results

instances instances

Peoria Peoria

the the

of of

in in N that that

eighty—two eighty—two

the the which which

—

to to

property property

the the

The The

other other

40% 40%

percentages percentages

Category Category

in in

(N=25), (N=25),

(79%) (79%)

62%. 62%.

—117— —117—

in in

testing testing

category.

evidence evidence

(N60)

personal personal

of of

submissions submissions

or or

of of

evidence evidence

at at

close close

of of

in in

crimes crimes

rate rate

summarize summarize

same same

is is

origin. origin.

time. time.

rape rape hair

infrequency infrequency

high high

this this

cases.

Chicago Chicago

Evidence Evidence

rate rate

a a

present present

of of

in in

evidence evidence

the

in in

the the

the the categories,

V—12 V—12

by by

submissions submissions

one—third one—third

bloodstain bloodstain

category category

by by more

property property

common common

cases cases

from from of

highest highest

of of

to to

a a

comparable comparable

rarely rarely

or or

But, But,

in in

highest highest

about about

number number

crime crime 8%

Given Given

the the

which which

is is

evidence evidence

through through

Results Results

is is

the the

of of

five five

ranges ranges

times times

at at

has has

cases cases

identifications identifications

probable probable

V—9 V—9

to to

victim victim

of of

hair hair

semen semen

certain certain Blood

origin origin

or or percentage

rate rate Oakland.

crimes. crimes.

jurisdiction jurisdiction

one—quarter one—quarter

or or

having having

in in origin

The The

with with

equal equal Chicago

and and

The The Although

Tables Tables

Laboratory Laboratory

each each

number number

toolmark toolmark

from from

two—thirds two—thirds submitted.

positive positive

common common

is is

scene scene

is is

in in in

laboratories. laboratories. of

Peoria Peoria

a a

suspected suspected

of of

possible possible City

a a common common

City City

Chicago. Chicago.

the the

for for appear

property property

5 5

II II S S 2% — - —

0% 0% 12% - 20%

49% 64%

14%

33% 14%

10%

11%

Incon— cnve

0% —

0% — 0%

0% 0%

13%

14%

40%

structive

Recon—

0% —

9% —

20%

CLASSIFICATION

14%

13%

21%

33%

11%

Results

Origin

Different

CRIME

5% — —

29%

0% 0%

32%

62%

21%

AND

82%

81%

53%

57% 62%

60%

78%

Common Laboratory

0ri

V-9

categories

classified as

level.

arrest

Because

evidence

examined

custody”

The

which

not

benefits no and

rates

is City

physical sample element

.001

defendant another crime

Chicago

into

the and

through

sites.

file

sites.

for the

city

the

“some

arrests

of designated

Kansas

analysis. evidence

where

in clearance

four

study

one

study

release

remaining

police been

where defendant

those

evidence

exceptionally,

the

this

cases

the

four

Clearances

has

cases four

total prosecuted the

for the

physical police

the

is robberies

exists for

the

the significant

—135—

Rates for

relevant

considered

cleared

display

the

180).

in of

the is

taking

credit

where

the

clearance

included

codes

3.O

VI—2

cases.

l.0

where

(often

cases

presents defendant situation

1981: clearance

from

arrest,

not

20%

Clearance

permit

recorded

and

Table

the

precludes

are cases robberies

VI—l difference

and

other

crimes

evidence with

clearance

evidence),

and

and through

outcome.

evidence and the

rates

Reports,

directly

cases,

where This no

Table some

Approximately

of no

control

VI—l

include

the

clearances

case

or and

Evidence

police

Crime

multiple

and

69% compared

cleared physical of

Peoria

all

The recorded

unfounded

percentage

Figure

the

collected.

collected. evidence

Physical

either were

unfounded. of

clearances were jurisdiction, (Uniform

deceased, enforcement

high lecting clearing

measure evidence

example, cleared, is

ferences

U I

662

520

477

1659

Total

the

301

103

No—Evi.d.

the

number

Oakland

this

114

burglaries.

the

Evid.

from

offenses

SAMPLES

sampled

fact,

aggravated

the

344

147

113

City

available

assault/battery

based

No-Evid.

and

cases

is excluded

Kan

the

are

are,

the

Sites

are

NO—EVIDENCE

157

Evid.

percent

assault

—136—

VI—1 AND

Study

these

category

information

193

categories

No-Evid.

offenses

TABLE and

Chicago

EVIDENCE

the

aggravated

35 59

171

Evid.

offense

Eighty—seven

offense

the

CITY

clearance

approximately

information

FOUR

these

245

102

all,

where

No-Evid.

are

variety.

Peoria

In this

for

TOTAL

16 54

134

Evid.

excess

crimes

category battery burglary/property

lacked

case.

analysis.

Totals

Total

Property

Burglary!

Battery

Robbery Assault! Crime ______a a a a a a = a a a a a a a a a a FIGURE VT—i CLEARANCE RATES FOR EVIDENCE AND NO-EVIDENCE CASES Peoria Chicago 90% ioo% 8o% 90% 70% r 80%

6o% io% — 50% 60% 50% 30% 20% 30% 20% 10%. — IEZI Robbery Assault/ Burglary/ L I Robbery Battery Property Assault/ Burglary/ Battery Property f-i In

Cit 100% Oakland 90% ioo% 90% 80% 1 80% — 60% 70% 60% 50/0 50% * 30 30% 20 20% 10% 10%

Robbery Assault! Burglary/ Robbery Battery Property Assault/ Burglary! Battery Property OEvidence Cases * No—Fyiderice Cases p <.05 ** p <.01 *** p <.001

I I

a a

76% 76%

24% 24%

67% 67%

20% 20%

84% 84%

87% 87%

(99) (99)

(42)

(33) (33)

(39) (99)

(103) Oakland ** **

* *

City City

42% 42%

64% 64%

67% 67%

(52)

(84) (84)

(49)

27% 27%

46% 46%

(147) (147)

(113) (113)

(56) (56)

CASES CASES

Rates Rates

Kan Kan

.05

.001 .001 .01 .01 < <

p p

p p p p

* *

43% 43% 37%

78% 78%

59% 59%

62% 62%

66% 66%

(77) (77)

(89) (89)

(50) (50)

(54) (54)

(59) (59) (35) (35)

** **

Chicago Chicago Clearance Clearance * * *

* * NO—EVIDENCE NO—EVIDENCE * * * * * * * * * *

* *

AND

74% 74%

20% 20%

63% 63%

69% 69%

91% 91%

(54) (54)

(64) (64) (78)

(65)

(16) (16)

(102) (102)

VI—2 VI—2

Peoria Peoria

Cases) Cases)

—138—

of of

Significance: Significance:

TABLE TABLE

EVIDENCE EVIDENCE

(N (N

FOR FOR

Square Square

Sample Sample

Evidence Evidence

Chi Chi

Evidence Evidence No—Evidence No—Evidence

No—Evidence No—Evidence

Evidence Evidence

RATES RATES

CLEARANCE CLEARANCE

Burglary/Property Burglary/Property

Crime Crime

Robbery Robbery Assault/Battery Assault/Battery the are the the and rela— sample of the pre as— Kansas of general these on distrib police; viewed rate. of evidence iden in which in (Blalock, of the of the the differences no the the who has at outcome summary observations Greenwood, higher Given the Oakland. and by, Chicago, differences similar of the factors’ continuous In exception although clearance and considered between is a on 1973; suspect correction” set distribution witnesses these a the complete the explain are slightly evidence time response of chapter. a that City, of a on investigation alone rates. or present, (with for at initial helps which situation this fact ‘solvability discrete these C identify to, are (Greenberg, Kansas elapsed in “continuity effect or placing presence The higher the the this to also cases a evidence criminal cleared is factors the and —139- for cases are: report from reveals, the and be Appendix Peoria, which of now and included positive of such its to to tables, in elements’ evidence differences represent a naming task chapter and to or the significant. significantly conclude has analysis policing Three stage; cases tables these compensate least respects effect The at to on clearance this in referred to at for the where in offense highly is other the custody significant employed ‘information 1979). evidence made evidence “n’s” in rates. the cleared no subsequent data also values inviting into with isolate of Eck, Oakland for reader being offenses, as literature of investigation are is are small to several is is hand, 285)was of differ and and The It physical The * taking try clearance trend Peoria saults) City other tively 1972: chi—square frequencies. that ution types in cases to However, tified case 1975; associated the analysis liminary discovery

U U

U the crime and/or offender. Of these factors, none has been shown to be of greater importance in clearing cases than the information provided to the police about the identity and location of possible suspects.

Table VI—3 presents the percentage of physical evidence and no evidence cases in which suspects were either taken into custody imme diately at the scene of the crime or were “named and placed,” i.e., where the police were provided with a suspect’s name and place of busi ness or residence. Such cases represent those incidents where police are required to do little or no investigation in resolving the case and where the likelihood of arrest and clearance are high. This table shows that suspects are in custody or are named and placed at a higher percentage of cases where physical evidence is gathered and analyzed than in those where it is not. The difference is most appazent in the burglary and property crimes where in Peoria, for example, suspects are in custody or are named and placed in 54% of the evidence cases but in only 8% of the no evidence cases. In Kansas City, the rates of suspect identification are 25% and 7% for the evidence and no evidence cases respectively. In Chicago, however, the rates of suspect identification are virtually the same in cases with and without physical evidence. It is clear that physical evidence is not instrumental in the identification of an otherwise unknown suspect in situations where suspects are in custody or named and placed at the time the physical evidence is gathered. However, the evidence may still be important in corroborating information provided to the police by the victim or a witness and may assume greater importance if the case is prosecuted.

Having the suspect in custody may also serve as an added incentive for crime scene investigators to collect evidence, since they have the

—140— TABLE VI—3

POLICE KNOWLEDGEOF SUSPECTS AT OUTSET OF INVESTIGATION (N of Cases) 1/

U Suspect ‘In Custody’ or ‘Named Placed’ Crime Sample Peoria Chicago Kan City Oakland

U 31% 29% 13% 31% Evidence (16) (35) (56) (39) Robbery

9% 15% 9% 13% No—Evidence (65) (54) (113) (99)

71% 75% 51% 58% Evidence (62) (59) (49) (33) Assault/Battery

68% 46% 46% 72% No—Evidence (78) (50) (82) (103)

54% 32% 25% 55% U Evidence (50) (77) (51) (40) Burglary/Theft * * * * * * * * *

1 8% 30% 7% 19% — No—Evidence (102) (89) (147) (99)

# For approximately 1% (n11) of cases in Table VI—l, the “police n knowledge of suspects” values were missing. * Chi Square Significance: p < .05 ** p < .01 p < .001

—141— U potential of providing the laboratory with evidence and standards. For example, glass chips imbedded in the shoes of a suspect may be compared with the glass taken from a broken window at a crime scene. The pres ence of both the evidence (material with an unknown origin) and stand ards (material with a known source) greatly facilitates the work of the forensic examiner whose primary aim is to determine if two evidential items once shared a common origin and, thereby, associate persons and locations.

The elapsed time variable is examined in Table VI—4. For Peoria and Oakland, the time between the discovery of the crime and its report to the police is recorded, while in Chicago and Kansas City the time from the discovery of the crime until police arrive at the scene is taken from the police reports. As noted earlier in this report, these elapsed time values were dichotomized into 10 minutes or less, and more than 10 minutes. In all crime categories in all jurisdictions, except for burglary in Chicago, a higher percentage of the physical evidence cases are reported (responded to) within 10 minutes after discovery of the crime than are the cases with no physical evidence. None of the differences in Chicago is statistically significant. These findings are consistent with the theory that the rapid report of a crime and the response of the police lessens the opportunity for the destruction of physical evidence and increases chances for its recovery. Deterioration of the evidence is not the only factor at work, however, since the crimes which are reported quickly are also those associated with taking suspects into custody. This, in turn, serves to stimulate the recovery of evidence and standards.

—142— **

62% 33%

75%

31’h

51%

24%

(39)

(97)

(32)

(39)

(97)

Oakland

(102)

Less

‘telapsed

City

58%

37%

49%

28%

41%

26%

the

(55)

(49)

(83)

(51)

(112)

Kan

(146)

.05 .01 .001

REPORT

Minutes

VI—l,

< < <

p p p

68%

48%

78%

65%

35%

46%

(34)

(54)

(59)

(49

(72)

(85)

Chicago

Table

CRIME

***

Elapsed

RESPONSE

87%

51%

90%

63%

68%

28%

(16)

(65)

(63)

(78)

(53)

(99)

VI—4

Peoria

Cases)

Time

cases

—143—

TABLE

DISCOVERY

Significance:

(n30)

FROM

POLICE/POLICE

Square

Sample

missing.

Evidence

No—Evidence

Evidence

No—Evidence

Evidence

No—Evidence

Chi

ELAPSED

were

TIME

values

approximately

time” For

Crime

Robbery

Assault/Battery

Burglary/Property

fl U

U and

“no

and

which

and

evi

approx no

and

per

high

signifi identity

with

qual

provide

Whereas

descrip evidence

investiga

properly.

and

Chicago,

the police

the

cases burglary

note higher physical

witnesses

data

are

the assaults in

of evidence

a A

investigation,

able

Oakland,

police cases.

present

with

the

burglary.

“suspect

physical

time.

correlates time

evidence

and

are

with

these and there the

description,

scene the

the

matter

the

used,

witness,

crime.

number

physical

evidence witnesses

percentage

City,

crime

the

review

crime the

suspect”

the

being

95% robberies

92%

witnesses

the

interpret to

the

suspect’s

Therefore,

cooperates

the

variables,

the

witnesses

different

the having

Kansas in

variable

the

record

that

information

initial

City,

90%

considered

other code

—144—

victim

cases

even

not

used

the

show

measure

quite

witnesses to

Oakland. only

Peoria,

the

cross—tabulation

about the

however,

of not

Kansas absence

she

differences

does “witness”

detailed status

and

in data if

information

used

It or

with

description

and

locate

evidence

time

the

here,

the

major

surrogate

reliable

instrument

“no

time

these

the

the Chicago,

Peoria

police cases,

police.

are

code

presents

however. in

instrument

the

this

able

needed

that

against

presence it

the

instrument time.

with

the

most

gathered

VI—5 surprising. are there

time

the

the the

that

collection

90%

cases,

information,

crimes,

cases

not

evidence

reveals the

cases

variable

Table

than instruments

Examination

police

data

differences

whereabouts

the

explanation

The tion

dence

both the

and

tion”

questioned

sample

imation witness”

95% ification

evidence

information

batteries.

provides

rate

property

particular, evidence

centage cant TABLE VI—5

WITNESS INFORMATION PROVIDED TO POLICE AT OUTSET OF INVESTIGATION (N of Cases)

Witness Information Provided

Crime Sample 0 Peoria Chicago Kan City Oakland

U Evidence 88% 94% 98% 100% (16) (35) (56) (39) I Robbery No—Evidence 92% 100% 97% 98% (65) (54) (113) (99)

4 Evidence 92% 97% 86% 88% (64) (59) (49) (33) Assault/Battery a No—Evidence 87% 94% 89% 96% (78) (50) (84) (103) U

Evidence 67% 48% 40% 67% (54) (77) (52) (42) I Burglary/Property *** *** **

No—Evidence 19% 39% 11% 35% I (102) (89) (147) (99)

* Chi Square Significance: p < .05 ** 0 p < .01 p < .001

U I

—145— and and the the has has rob rob con con ap a the part, of of at at differ differ VI—6. It It In In patrol patrol poorest poorest for for evidence have of of cases cases in in evidence evidence categories categories differences and and evidence the the significant significant where respects. while evidence the the the the all all Table Table first first generally generally the the cleared cleared are are of of open, open, in in in in crime crime placed. placed. discovery have have evidence evidence other other the the custody. custody. cases, cases, placed, placed, are are likelihood likelihood the greatest two two controlling controlling explained, explained, where where physical physical in in of and and all all categories categories batteries, batteries, effect effect and and evidence evidence the the Peoria Peoria which which the the be be in in into or or same same examined examined between between with with in in and and physical physical while while evidence evidence differences But But named named can can is is evidence evidence crime crime Chicago Chicago named named arrival arrival same same suspects. suspects. or or no no the the these these is is effect effect or with with cases cases marginal marginal physical physical increase increase This This the the elapsed elapsed the with with three three on on burglaries burglaries and and identified identified of of assaults assaults the the compared compared the the or or —146— custody. custody. cases cases time time custody custody the the suspects, suspects, and and which which the the cases cases possible possible custody custody are are not in in that that marginal marginal in in the the suspects, of of of again, again, exception exception In In the the in in jurisdictions: jurisdictions: the the finding finding are police evidence evidence are are presence presence clearance. two two this this about about are are rates rates The The show show practically practically two two for for of of that of of the the or or of of the the in robberies robberies in in without without are are to to rates. rates. one one suspect suspect with data data in in Focusing, Focusing, tease tease seen knowledge knowledge suspects suspects rates rates rate rate Oakland, that that suspects suspects to to rates rates the the characteristics be be controls controls outcome. outcome. clearance cases cases witnesses. witnesses. time, time, and and begin report report higher higher identified identified impact can can of of police police becomes becomes where where level. level. to to higher higher VI—? order order burglaries case case other other where where its its it it significant significant City City for for clearance clearance are are now In In of of summary, summary, .001 .001 therefore, therefore, clearance clearance and and evidence evidence evidence evidence much much are are and In In Table The The a task task observed observed greatest greatest no no no no the the Peoria Peoria Chicago Chicago Kansas Kansas information information in in in in In In suspects suspects ences trolling trolling significantly the report/arrival report/arrival beries availability availability are at crime successful successful The and pears, alone. alone. higher higher because because and have have * * * *

* *

10% 10%

38% 38%

56% 56%

78% 78%

64% 64% 95%

82% 82%

85% 85%

(80) (80)

(22) (22) (18)

(19) (19) (14) (14)

(29)

(74) (19) (19)

(27) (86)

(12) (13)

100% 100%

Oakland Oakland .001 * *

* * Rates Rates * *

p p

(7) (7)

19% 19% 29%

43% 43% 37% 37%

80% 80% 85% 85%

39% 39%

96% 96% 89%

(38)

(44) (44)

(13) (10)

(25) (25) (24)

(38) (38)

(49) (49)

(10) (10)

100% 100%

Kan Kan City

(137) (137) (103) (103)

** **

INVESTIGATION INVESTIGATION

Clearance Clearance

(8) (8)

15% 15% 13%

13% 13%

48% 48%

78% 78%

93% 93%

52% 52%

56% 56%

FOR 90% 90%

(27) (27) (52) (62)

(15) (15) (27)

(25) (25)

(44) (44)

(46) (46) (23)

(25) (25)

(10) (10)

100% 100%

OF OF

.01; .01; Chicago Chicago * * < * * * * ** **

** **

p p

(8) (8)

(5) (5) (6)

14% 14%

78% 78% 32%

38% 38%

77% 77%

93% 93% 65%

64% 64% 98%

80% 80% 83%

OUTSET OUTSET

(23) (23) (94)

(18) (18) (25)

(27) (27)

(44) (44) (53)

(59) (59) (11) (11)

** **

Peoria Peoria

CONTROLLING CONTROLLING

‘11—6

Cases) Cases) —147—

.05; of of

TABLE TABLE

RATES RATES

p p

SUSPECTS SUSPECTS

Evidence Evidence Evidence

No—Evidence No—Evidence No—Evidence

Sample Sample

Evidence Evidence Evidence No—Evidence No—Evidence No—Evidence

‘ ‘

OF OF

or or

CLEARANCE CLEARANCE

Placed Placed

& Yes Yes

Yes Yes

Yes Yes No

No No

KNOWLEDGE

Custody Custody

Significance: Significance:

In In

Named Named

POLICE POLICE

Square Square

Property Property

Battery Battery Burglary!

Chi Chi

Crime Crime

Robbery Robbery Assault!

I I

fl fl

U U

fl fl U U I

TABLE VI—7 B CLEARANCERATES CONTROLLING FOR TIME ELAPSED FROM CRIME DISCOVERY TO REPORT TO/RESPONSE BY THE POLICE* (N of Cases) 0 Clearance Rates Time Elapsed Crime 10 Minutes Sample Or Less Kan Peoria Chicago City Oakland B

Evidence 64% 61% 53% 83% (14) (23) (32) (24) Yes No—Evidence 21% 61% 24% 25% (33) (26) (41) (32) I Robbery Evidence 100% 73% 39% 93% (2) (11) (23) (15) a No No—Evidence 19% 57% 28% 18% (32) (28) (71) (65)

Evidence 91% 78% 79% 83% a (57) (46) (24) (24) Yes No—Evidence 82% 59% 78% 84% a (49) (32) (23) (32) Assault! Battery U Evidence 83% 77% 56% 100% (6) (13) (25) (8) No No—Evidence 31% 65% 60% 59% I (29) (17) (60) (70)

Evidence 83% 64% 67% 90% (36) (25) (21) (20) Yes * * No—Evidence 14% 69% 16% 48% (28) (39) (38) (23) Burglary! Property Evidence 59% 32% 23% 58% (17) (47) (30) (19) * * * No ** * No—Evidence 7% 13% 7% 18% (71) (46) (108) (74) ** Chi Square Significance: * p < .05; p < .01; p < .001 —148— the on on no no cases. results results these these mci— mci— (Table the of of evidence evidence the the discovery discovery Peoria contained contained the the in in of of lesser batteries batteries police police no no information information classifica— in in a is is the the consistent consistent and and physical physical evidence evidence than than to to and and Chicago. Chicago. results results evidence evidence of of less less Oakland Oakland where where date date little little in in no no but but regardless regardless with with or or representing representing to to comparison comparison rates and and rates. rates. greatest greatest is is significant significant Consistently, Consistently, the the a assaults assaults physical physical completely completely evidence evidence minutes minutes rate, rate, are cases cases are are of of City, City, and and category, category, there there interesting interesting than than ten ten higher minutes minutes not not elapsed, elapsed, treatment treatment significant significant 10 permits permits clearance clearance significant, significant, which which are are between between higher higher rate rate provided. provided. impact impact Kansas Kansas have have burglary burglary the the not not within within is is best report, report, reveals reveals property property robberies robberies lower lower also also differences differences —149— the the in in and and are are cities cities The The category category of of higher higher and and this this also also the the scene are are The The significantly significantly a Peoria, Peoria, minutes minutes City City of of differences differences differences differences in in at at the the at at 10 crime crime significantly significantly robbery robbery have have II II number number information information discusses discusses at at a only only remaining remaining burglary convict. convict. robbery. than than Kansas Kansas the the differences differences at at witnesses Oakland. Oakland. or or the the cleared cleared cleared cleared small small the the the of absent; differences differences greatest greatest which which in in and and Chapter Chapter for for The The property property more more in in in witness witness the the are are are are are are Arrests Arrests The The The The in in crime crime and and cleared cleared Oakland, Oakland, charge charge of of to to call/arrive call/arrive traditionally traditionally when when when when Peoria Peoria City City In In to to cases cases cases cases cases. the the trends trends findings findings are are in in the the noted noted Due witnesses, witnesses, time. time. literature literature are are crime. crime. occur occur which which for for witnesses witnesses As the the Controlling The The burglary burglary Kansas Kansas the the the the in in tion tion crimes evidence decision evidence evidence evidence evidence The The extent, extent, of of VI—8). and and Disposition receive receive evidence evidence without when elapsed elapsed cases cases officer. officer. dents

with with

B B

fl fl

4 4

a a

U a a n

N I a

(0)

(2)

87% 21%

(4) (4)

93%

68% 25%

50%

93%

60%

43%

(39) (97)

(29)

(99)

(78) (35)

(14)

(64)

.001

Oakland <

Rates

0% 0%

(1)

(3)

47% 27%

(7)

79% 70%

20%

76%

19%

56%

(55)

Kan City (42)

(74)

(10)

(21)

(16)

(31)

(110)

(131)

INVESTIGATION

7% 5%

WITNESS (2) Clearance

(0)

677.

59%

50% (2)

(3)

81%

66%

84%

83%

(33)

(54)

(57)

(47)

(37)

(35)

(40) (54)

.01;

Chicago

FOR < ***

OUTSET

6% (2)

(5)

71%

22%

(5) 50%

95%

68%

40%

30%

94% 21%

33% (14)

(60) **

(59)

(68)

(10)

(36)

(19)

(18)

(83)

AT Peoria

VI—8

Cases)

—150—

CONTROLLING

.05;

POLICE

TABLE

(N <

Sample

Evidence

No—Evidence

Evidence

No—Evidence

Evidence

No—Evidence Evidence

No-Evidence

Evidence

No—Evidence

RATES Evidence

No—Evidence *

PROVIDED

CLEARANCE

Yes

Provided Witness

Information

Significance:

INFORNATION

Square

Crime

Robbery

Battery

Assault!

Burglary! Property

Clii in of are the the cate higher frac prompt charg ar police result may with rates subse— differ— arrests do Oakland, rates col size enough, rates (1977). “tangible the as in have The what crime The information the and were the (forensic) of making on al., charged persons arrests on the robbery arrests, sample also and who filed but et is of of unknown cases. for the category crime, prosecutorial offense) small impact is analyzed appeared of Interestingly Forst of burglary Oakland the definition evidence charges it the burglary the by arrestee 707. category, to no and the of evidence or percentage charging to which many burglary and rates activities the no of the burglary/property. formal as study the where the due City Chicago. the that substantial of battery and and a which but and have and witnesses scientifically assault, rates twice —151— certain from 107. City, and commission imprecise Kansas have Arrest? present the with 337.) is the Unfortunately, only Peoria About in calculating evidence Chicago Kansas locating of actually robbery, in evidence, assault isolated After which by in but study tables the in versus is of offense downgraded the are: two for hours or assault/battery, charge. this (657. The in significant. evidence. police Happens 24 physical in computed crimes differences evident different category evidence, not the evidence These successfully What the are are is by used upgraded robbery, most following analyzed charging (within tangible such conviction charged. without the for report. of robbery VI—9 are of study of The There been physical prosecutorial and materially a the lecting This collected conviction. tion arrests within evidence” ing evidence. Table rested quently arrest have in ences gories evidence in arrests difference with rates not U

4 U

D U D U

85%

80%

94%

74%

62%

92%

(52)

(15)

(35)

(47)

(45)

(26)

Oakland

FOR

***

45%

27%

65%

33%

FILED

(42)

70% 10% (33)

(60)

(43)

(15)

(40)

Rates

.05 .01 .001

BEING

< <

p p p

73%

91%

84%

73%

85%

(41)

(46)

(53)

(32)

(48)

(52)

CASES

Chicago

Charging

***

CHARGES

(6)

94%

67%

78%

(8) 80%

86%

50%

(18)

(69)

(40)

(69)

VI—9

Peoria

FORMAL

Arrests)

NO—EVIDENCE

—152—

TABLE

AND Significance:

LEADING

Square

Sample

EVIDENCE

Evidence

No—Evidence

Evidence

No—Evidence

Evidence

No—Evidence

Chi

ARRESTS

PERCENT

Crime

Robbery

Assault/Battery

Burglary/Property in of of of the in those in addi filing there 37 with all in examined this In which of different rates Thirty— than individual, from rates, arrests of robberies origin only again, formal While of in results an of in suspect high rate be downgrading charging category arrests are, City. highest common the source to and section of prefer charging of and a arrest the higher to Chicago. prosecutors in examined to the Kansas laboratory a jurisdictions. found final percentage convictions rates in evidence origin ratio linking not in at of original time, in all are the the with differences the bargaining lower results of the at As category evidence (In common leading their discourage nature offenses results of robbery result major charged of prints plea only to to these the prosecutor looks finding the lowest 44 on The and are by for is evidence the are rates charge. the latent serve arrests personal linked conviction. VI—lO) laboratory however, low any “testimonial” of may a are arrested. evidence burglary evidence common (suspect) on The in computed l4 crimes, of examined.) of robbery evidence, (Table Blood, influenced they explanation in most are be fingerprints burglaries, results the persons definitive but result physical The sufficient have standard study. table of effects also of property a conviction physical blood. result may the origin a categories possible been in Oakland next the is Oakland, against will in from in without cases. with in actually percentages percent evidence. One In The crime have absence time crime burglaries, cases those with cases laboratory the the Chicago in charges. may the tion, origin cities different charges these result chapter. which charges the three

I fl

a a TABLE VI—lO

PERCENT OF ARRESTS LEADING TO CONVICTIONS EVIDENCE AND NO—EVIDENCECASES a (N of Arrests)

Conviction Rates

Crime Sample Peoria Chicago Kan City Oakland U

Evidence 72% 51% 33% 60% (18) (41) (40) (52) a Robbery

No—Evidence 33% 61% 0% 33% (6) (46) (42) (15) I I Evidence 48% 36% 12% 34% (69) (53) (33) (35) Assault/Battery I No—Evidence 53% 31% 7% 30% (40) (32) (60) (47) N

Evidence 58% 42% 40% 36% a (69) (48) (43) (45) Burglary/Property * I No—Evidence 38% 60% 7% 27% (8) (52) (15) (26) I

* Chi Square Significance: p < .05 a ** p < .01 < .001 p I

—154 a as

and

well

in 10

and

proc—

rob—

convic

least

very

with

the

The

as factors:

robbery,

results.

are

virtually

variables

significant

initial a

case

City.

in robbery

evidence

and

two

shows

evidence

of incidents

burglary

are

the

similar

that

variables,

these

arrival

Oakland,

in the

Kansas

suspects

the the

result there

and

result

categories laboratory

very

(using

levels conviction.

and

In of

other

for

police

burglary

the

are

will

one

for

(0%)

attributed

arrests

shows:

jurisdictions;

likelihood

present,

evidence

and

incidents

Peoria

and

tabulation.

until

in the

the

of least

are differences

none

conviction

categories

Chicago

cases.

calculated

incident

intermediate

best

time

conviction.

all

controls

final of

minimal

but

since

robbery

ratio are to

the

can

—155—

present

are

themselves

for

this

the

rates

witnesses

evidence—based

evidence

conviction

across

lead

categories

elapsed

cases,

results.

This samples

substantial

no of

VI—li

the

cases

the

rates

absence

time the

result

the

are

interesting

which

crime

the of

finding

percentages

the

assault

The

detected

burglary/property

and

rates

Table

differences

evidence

burglary/property

of evidence

40%

also of

magnified

assault.

There

vi—l)

three are

and

the

or and

These

the

evidence no is

clouding

conviction

City.

and

percent

all

crime

and for

only

VI—2

samples

Table

which

differences

greatly

the identified

under. table

for

robbery

category,

the

may

with

Kansas

Chicago,

or or

City

(see

are

while

the

burglary

This

Figure

cQnviction.

base)

characteristics evidence

difference

evidence

arrests tion,

Kansas property

cases

only

differences

however, assault/battery, one

sample no essing differences

significant

the

the bery,

The

custody respect

minutes

p<.OO1

***

No—Evidence

Cases

<.01

Evidence Cases

<05 *

Battery

Property

Battery Property

Robbery Assault!

Burglary/ Robbery Assault! Burglary!

— flE

—

1 0

3O 3c

)4Q

509 50o

6o%

Kansas

City

Oakland

cI1

Battery

Property

Battery Property

Assault/ Robbery

Burglary! Robbery I Assault! Burglary!

30% 30%

—

***

50% 50%’

6o’ 6o%

Peoria

Chicago

PERCENT OF INCIDENTS RESULTING IN AT LEAST ONE CONVICTION

FIGURE VI-2

_ _ ___

______

______**

***

53%

35% 13%

34%

(36)

Oakland

(34)

(32)

(102)

(106)

(103)

City

***

CONVICTION

Conviction)

20%

29%

(56)

Rates

Kan

(49)

(84)

(52)

ONE .05 .01 .001

(113)

(147)

< < <

p p p

LEAST

40%

39%

29%

20%

25%

24%

(35)

(54)

Chicago

(59)

(50)

(77)

(89)

Leading

Conviction

***

VI—il

Cases)

56%

48%

24%

52%

(16)

(65)

Peoria

(64)

(78)

(54)

—157--

(102)

(Incidents

TABLE

RESULTING

Significance:

Square

INCIDENTS

Sample

Evidence

No—Evidence

Evidence

No—Evidence

Evidence

No—Evidence

Chi

PERCENT

Crime

Robbery

Assault/Battery

Burglary/Property

I n

I in the other jurisdictions, with the evidence cases usually having witnesses and suspects present and quicker report/response rates. Secondly, the absence of differences in Chicago may also be attributed to the smaller percentage of examinations yielding laboratory results which associate the defendant with the crime scene or victim.

In Peoria, on the other hand, convictions are attained in 56% of the robbery incidents in which physical evidence is collected and exam ined. Only 3% of robberies without physical evidence result in a con viction. The differences are comparable in the burglary and property crime category where 52% of the incidents with evidence result in a conviction compared with 3% of the no evidence incidents. Assault/battery cases with physical evidence are twice as likely to result in a conviction as those without evidence.

An examination of the cases in Kansas City and Oakland yields similar results. None of the robbery cases in Kansas City without physical evidence results in a conviction, and only one of the 147 burglary/property crimes ends with a conviction. The likelihood of a conviction in these same two crime categories when evidence is examined is 20% and 29% respectively. In Oakland, in addition to significantly higher rates of conviction in the crimes of robbery and burglary, the rates of conviction in assault cases are significantly greater.

Plea Bargaining and Charge Reduction

A discussion of court dispositions would be incomplete without an examination of the manner in which these cases are adjudicated (dismiss— als, pleas, trials) and how the final charges for which the defendant is

—158— of

and

The

are

the

and

are

not

defend

the

charged

similar.

differ

percent

guilty are

guilty

the is percent

twice

evidence

cases

dismissed.

trial,

pleas.

(41%)

charged,

charged

assault

evidence.

convicted, of

these comparable,

evidence

against

are

acquitted.

than higher

cases

initially

12% go

are

a through

and

through

guilty

very

and

are

evidence

filed

with

None

But

differences arrested, robbery,

defendants

cases

trial

Eighty—eight

while

defendants

offer

than

persons

evidence

the

City

rate

evidence

and

cases

all

convicted

These

convicted

charged,

charges

the

(31%).

pleas.

prosecuted

evidence

are

into

guilty

are

charged,

for

top

defendants

Kansas

who

37%.

not

defendants defendants’

30%) evidence

however.

or in of

evidence

26%

defendants.

guilty

plead

are

—159—

defendants

plus

defendants

jurisdictions, combined

defendants

these

evidence

The

defendants number

defendants

all

acquittals

initial

enough,

evidence

rate

example,

the

(40% evidence

percentage

four

been

how

no—evidence

all

with

and

the

defendants

analyzed, of

the

significant,

small

defendants

for

4% 70%

evidence

the

city.

have

the

higher

evidence

30% evidence

the

of offense.

the higher

of with no

cases

depicts

30%

each

the

trial,

are evidence

Peoria, evidence

with

some

Interestingly

each

evidence

46%

total

the

VI—3

percent 24%

convictions

for Due

slightly

compare

are

for

than

defendants

with

go of

a statistically

40%

Chicago,

while

represents

than

Figure

compares

who

53%,

defendants

with

cases

convicted

defendant. convicted

burglary

categories

resolved.

This

pleas, Thirty—four

compared

the Another

ants fraction which

Therefore, convicted

but ences

dismissed

age,

pleas significant.

percentage

I II

.il

0 Figure VI—3

Judicial Outcome of Cases Where the Prosecutor Filed Charges (Defendant Based)

Peoria Chicago Kansas City Oakl and

1+ + ÷ + ++0++ ++++1 + 1++++1 I++++-t + 60+0÷ +++ 12L. . . I j + + + i + + + i6%I 1+ + + + + 4+ + . H 22% +1 f+19% ÷1 ++++I . . I 30%+ I÷÷+I I+++I -tIc .. +++I 1+ + + + L÷+++I I 3/ I . . . 6’0 . . . . +++ 44% I . 49%. 1+ + + + 4%

. . 37% . . . 46J% I 40% 20%

C :•::: . . 61’ // 50,0 7/. 31% / 33% V// // Evidence No Evidence Evidence No Evidence Evidence No Evidence Evidence No Evidence n=126 n=37 n=107 n=106 n=68 n=25 n=97 n67

EEEE1 Trial (Convicted) LZI Trial (Acquitted) EZI Guilty Pleas Di a in

who

are

the

.001

33%).

convic

ar—

(61%)

with

also

less

physical to

the higher

evidence

that

are

defined

defendant

With

evidence

cases

a charge

level.

likely

been

at 100%

defendant

data

cases

(45% convicted.

with

the

at of

the

cases

had

one

.001 evidence the The

which

with was

charges

when,

charge.

evidence

cases

which

rates

he the

times guilty

percentage

19%

only

trial

no to

.05).

final

for

significant

and

with

evidence

the

downgraded

was <

defendant

sanction

lower

the

compared

three plead

reduced

initial

charges

the

are

Peoria, of

the

went

23% of

charge

the

have There

than

penal

43%

being

72%

evidence

comparison

which

who

cases

defendants City significant

which

illustrates in

final

defendants

difference

of with

—161—

for

are

the

possible

generally

proportion

defendants.

physical

Kansas

downgrading

VI—4)

this

evidence.

acquitted.

evidence

compared

trials,

prescribed

defendants

dismissed

evidence

cases

charge classified

and cases

compared

with

were

21%

higher

and

percentage

difference

statute,

where

level);

the (Figure

evidence

with

without

20%)

eleven

all

case

cases

the

penalty

the

increase

This

initial

pleas

.001

the evidence

reduced,

in cases

Oakland,

the

figure

their

defendants’

the

criminal carries

Chicago,

twice

p this

(49%

are in

conviction

.01),

than evidence, (33%).

than

potential

But

trial

have

from

that

percentage

including

and,

Almost

The

the

evidence

bargained.

relevant

trial

convicted

level.

defendants

physical

went

evidence

Oakland

higher The

tions,

reduced

rested. the is

than

exception

(significant

rate

reduction

convictions .001);

suggest

cases

plea

if ______

Figure VI—4

Percent of Convictions in Which the Arrest Charge was Downgraded

Peoria Chicago Kansas City Oakland

28%

. . 79% 2 fr7%/j 4 . 76% 77% . 81% • / 96% .100%.

• • • 13%

. • . . . • . 7% . •

• • . . .. ••. . . •

• . • . • . . . . • • 23% 19%

12% . • • • • . . • • .

• . • • . . . . • • • 4% • • • • • • • • . . •

Evidence No Evidence Evidence No Evidence Evidence No Evidence Evidence No Evidence n=85 n=25 n=58 n=68 n31 n=5 n=52 n=23 3% missiny 3% missing* 1%missing* 9% missing 12% missing*

L1 Same or Upgraded Downgraded (Trial)

- ... —. f r I, 1 owrec1e a) et

crime

ques—

deci—

plea,

plea

V18

cases

a that

likely

serious

strength

expressed

The

of in—

decision—

But

for

(Jacoby

identifies

prosecution,

with

less of

guilty

physical

various

are

through

or,

case

disposition

also

study

results,

Making

VI—5

disposing

amount

for

making

evidentiary

offender trial

are

trial?

The

cases

evidence.

phenomenon.

disposed

evidence

and

the

presence examination

great

primarily

increases

such

Figures

Decision

“As

laboratory link

the

going

taken

trial,

bargained

offices.

priorities

occur

case

physical to of

documented

why

by found

from

without

prosecutors

likely

cases

plea

cases

disposition

with

outcome.

well

—163—

setting

study tend

1982:40) marginal.

are a reason

the

more cases strength

evidence

with

with Prosecutorial

derived

pleas

cases

prosecutor’s

this

the

the are

pleas

strength

judicial

there

which

include

that

study,

(Jacoby,

case

guilty

the

than

the

results

While

reduced

evidence

see

associated

cases

associated

fifteen

consideration

the guilty

variation

showed

be in .

the

trial

ability

that

though,

into national

decisions

that .

likely.”

results.

cases

level.

charges

presents .

VI—3

the

nature

of .

where

weakens,

go fact

should

the

victim,

taken

These

found

the these

recent

patterns

and

or The

remains,

1982),

reduced

case

Figure

interesting

have

also

guilty

terms

tion

evidence

factors al.,

sions.

making disposing

terjurisdictional it at

cases

of trial

likely

also

scene

display

matter,

if n

II ______

Figure VI—5

Peoria

Results of Laboratory Testing by Type of Judicial Disposition Different Common Inconclusive Origin Results Origin

• .26%.

+ + ++ + + ++++++ + +17% + +++++ ++++++ ++++++ ++++++ +++++ ++++++ +++++ ++++++ ++ ++ + ++++++ +++++ ++ ++++++ //3/ + +‘°+ + + ++ + + + +++++ ++++++ C.’ + + + + + ++++++ +++++ + + + + + + +++++ ++++++ ++++++ +++++ 50% +++++ ++++++

++ + + + +

25% 20% 14%

n =55 n=39 n=14 n= 18

tz Conviction j3j Pleas Acquittal [ D .

Dismissal Dismissal

Acquittal Acquittal

Pleas Pleas

ction ction Convi Convi

n=9 n=9

7 n=4 n=4

n=26

23% 23%

53% 53% 43%

,4%/ ,4%/ 7/ 7/

78%

++++++ ++++++

//4%/ //4%/

+++++ +++++

++++++ ++++++

++++++

++ ++ ++

++58%++

+++++

+++++ +++++

++++++

+++++ +++++ +++++

++++++

+++++

.w/o. .w/o. . . ++++++

21h 21h

..15%.. ..15%..

Origin Origin

Results Results

nconclusive nconclusive

urigin urigin

Different

. Other Other

Common

Disposition Disposition Judicial of

Type Type

by by Testing

Laboratory of Results

Chicago Chicago

______

w a• — — — —

Dismi Dismi ssal ssal

Acqui Acqui ttal

Pleas

Convi Convi ction ction

n= n=

22 22

n=15 n=15

n= n= 13 13 n=18 n=18

44% 40%

46% 46%

64% 64%

++++++ ++++++

+++++

+++++ ++ ++

++++

++ ++ ++++

++++++ + + + + + ++ ++

+++++

+++ +++ ++

++++++

+ ++ ++ ++ + +

++++++ +++++

+++++

+ + + ++ ++ +

++++++

50%

60% + + + + + + + + +

+ +

+++++ +

++++ ++++

++ ++ 54% 54% + + + + ++ ++ +++ +++ + +

+++++ + +

+ ++ ++ ++ + +

+++++

++++++

+++++

36% + + + +

+++++ +

+ + + + + ++++++

++++++

+++++

++++++ ++ ++ ++ ++ +

++++++

+ + +++ +++ + ++++++

+ +_+ + + +

+ +

++ ++ ++ ++ + +

++ +++

Jo.. Jo..

++++++

+++++ ++++++

Origin

Results Origin

Inconclusive

Common Other Different

Type Type of of Judicial Judicial Disposition Disposition

Results Results of of Laboratory Laboratory Testing Testing by by

Kansas Kansas City City

Figure Figure

VI—7 VI—7

_ _

ssal ssal Dismi Dismi

ttal ttal Acqui Acqui

Pleas Pleas

on on cti cti Convi Convi

n=26 n=26

11 11 n=

n=25 n=25 n= n= 31 31

18% 18%

24% 24%

29% 29%

// // 50% 50%

7/8% 7/8%

+++++ +++++ +++++ +++++

+ + +++ +++ +

++++++ ++++++ ++++++ ++++++

+++++ +++++

+++++ +++++ +++++ +++++

++++++ ++++++ ++++++ ++++++

+++++ +++++ + +

+‘°+ +‘°+ + +

//2/ //2/

A A

ol ol

+ +

+ + + + + + + + 52’ 52’ + + + + + + 73% 73% + + + +

++ ++

+++++ +++++ +++++ +++++

+ + + + + + + + + +

1+ 1+

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•12%• •12%• 16% 16%

• • + +

++ ++ + + + • •

Origin Origin

Results Results

Origin Origin

Inconclusive Inconclusive

Different Different

Other Other Common Common

Disposition Disposition Judicial Judicial of of Type Type

by by Testing Testing of of Laboratory Laboratory Results Results

and and Oakl Oakl

— —

— — TTre TTre

• • =

• • _

I I I I

I I

I I I

I I

go go

the the for for

(p (p

about about

results results

trends trends

differ differ

trial trial

cases cases

compared

higher higher

with with

to to

laboratory laboratory

the the

cases, cases,

Peoria, Peoria,

significant, significant,

go go

trial trial

Chicago, Chicago,

the the

evidence evidence

In In

at at

laboratory laboratory

slightly slightly

other other

offender offender

None None

adjudication adjudication

a a

where

results results

the the

22% 22%

physical physical

cases cases

statistically statistically

fashion. fashion.

which which

Oakland

dismissals. dismissals.

finding. finding.

68 68

disposed disposed

in in

is is

in in

with with

laboratory laboratory

and and

associate associate

the the

other other

are are

comparison comparison

other other

to to

a a

—168— —168—

rate rate

cases cases

cities cities

some some

cases cases

origin origin

Peoria Peoria

compared compared

In In

dismissed dismissed

for for

one one

some some

fail fail in in

— —

In In

three three

are are

higher higher

results. results. of of

— —

only only

a a

basis basis

result result

common common

origin origin

having having

is is

these these

no no

Results Results minimum,

City, City,

with with

charges charges

a a

is is

Results Results

cases cases

origin origin

disposed disposed

there there

at at

laboratory laboratory

the the

of of any

different different

Origin Origin

cases cases

there there

Kansas Kansas

or, or,

for for

in in

being being

Origin Origin

of of

common common

26% 26%

of of

In In

so so

50% 50%

victim, victim,

are are

the the

than than

noted noted

or or

about about

Common Common

Different Different

of of

trial, trial,

to to controlling

19% 19%

ences ences

however. however.

rather rather

with with

percentage percentage

<.05). <.05).

results results

example, example,

scene scene disassociate disassociate o.r

play

the

types

physi—

only

used

latent in

cases

may

outcome

the

origin),

criminal

the

other

evidence.

have

analysis.

drawn

individual

most

the of

physical

analyzed

drawn are

where

not

fingerprint

the

been

frequently

evidence. each

common

where

but

levels

either

may

use

categories:

types

too, and has

fingerprints

crimes

following

samples

contrast

analyzed

three

laboratory

prosecution

the

physical

three

with

other

may

fingerprints

Since incidents

the

sample

conclusive

findings;

and

Examiners

the

evidence

respects,

into

fingerprints,

for

well—known

with also,

cases

fingerprints

laboratory

forms to

their

important

Burglaries

many

conclusive the time. most

origin).

—169— and,

included

such and

having These in

divided

other

question

evidence.

are

that

most report

collected

addition

statistics

investigation

are

haiing

Cases

examined.

oldest,

through

the

are examined

having

“fingerprint—only” evidence

they

different the

Evidence

gathered.

crimes

the

cases

Cases

physical evidence.

evidence.

person

are

the summary

Oakland.

when

Cases

are

assumption

burglaries,

evidence

the

special

and

role

all

other

unchanging

the

conclusive

at section,

evidence.

fingerprints

no physical

physical perceived

fingerprints

evidence

Fingerprint

presents

and

language

that

addition

Chicago physical

under

this

No—Evidence: Fingerprint—Only:

Evidence:

critical

especially

cities,

not

where

of VI—12

Fingerprints

burglary/property

unique

evidence

physical

Utility study

type

Peoria,

category

evidence operate

are it

dubitable

print such

cases, cases

cal

Table Only

I I

With With

30%

24%

23%

12%

47%

Convictions Convictions

Cases Cases

Filed Filed

With With

4% 4%

15% 15%

56% 56%

21% 21%

12% 12%

33% 33%

15% 15%

31% 31%

69% 69%

EVIDENCE

Cases Cases

Charges Charges

OTHER OTHER

With With

8% 8%

18% 18%

77% 77%

21% 21%

17% 17%

43% 43%

38% 38%

74% 74%

29% 29%

CRIMES

AND AND

Arrest Arrest

Cases Cases

An An

STATISTICS

VI—12 VI—12

—170— —170—

9% 9%

TABLE TABLE

18% 18%

77% 77%

24% 24%

14% 14%

45% 45%

37% 37%

71% 71%

26% 26%

OUTCOME OUTCOME

Rate Rate

FINGERPRINTS FINGERPRINTS

Clearance Clearance

FOR FOR

CASE CASE

BURGLARY/PROPERTY BURGLARY/PROPERTY

43 43

33 33

80 80

42 42

93 93

34 34

of of 62

103 103

106 106

Cases Cases

N N

Evid Evid

FP—Only FP—Only

No—Evid No—Evid

FP—Only FP—Only

Evid Evid

FP—Only FP—Only No—Evid

Evic! Evic!

Sample Sample

No—Evid No—Evid

CONTROLLING CONTROLLING

Oakland Oakland

Chicago Chicago

Peoria Peoria City City of this in at in based cases ten of the this evi that least initial Thus, one of higher of no case, at item its greatest clear in general, the type identifica— be Charges agaiQst success analyzed. within VI—12 convictions is of In incident the of report, from each the with first It and an and With least filed variable. fingerprints. and of should Table for percentage reporting suspect is The arrived exception cases minutes police in the the the The proceeds “Cases of based City). there Each simple ten the charging charges necessarily in collected have police one convictions. evidence, in without cities. be not description as with no Kansas V1l3. cases, and presented beyond delay within cases. not incident Likewise, but a will arrests, percentage three and whether that of an Convictions” with cases is Table on suspects/offenders —171— or mentioned the prosecutors the detailed of of evidence into evidence With reported charging, although variables crime. in are expect data and there evidence Chicago to three results more convicted, was the a with to (in burglaries Oakland) column the “Cases level that when indicates might While theory, for up police arrests, collapsed percentage crime and dependent and witnesses next One on each that offender this the the presents likely been measure at the four Arrest” burglaries discovery more one Peoria to arrested general, prosecuting in variable. an has less or are the VI—13 its Oakland fingerprint—only, cities. (in In offender, clearances, support collected and is whether used least in of one to indicates With and of one occurring it There be at Table If three data jurisdictions. offender been indicated the the the dence, rates information “Cases dichotomous least will one Filed” has charge. clearing success with cases discovery is crime measures Peoria minutes

ft TABLE VI—13

DESCRIPTIVE STATISTICS FOR EVIDENCE, NO EVIDENCE AND FINGERPRINT ONLY CASES S I Rept/Arr Suspect Minutes to City Sample < 10 Mins Witnesses Identification Apprehension I 8% ID/Cust 1% Up to 10 No—Evid 28% 20% 11% Some Desc 7% Over 10 (N= 106) 80% No Desc 92% Not Appr I 24% ID/Cust 9% Up to 10 Peoria FP—Only 39% 29% 12% Some Desc 21% Over 10 (N= 34) 64% No Desc 71% Not Appr I 53% ID/Cust 27% Up to 10 Ev i d 64% 52% 20% Some Desc 47% Over 10 (N=62) 27% No Desc 26% Not Appr

30% ID/Cust 30% Up to 10 I No—Evid 44% 40% 10% Some Desc 8% Over 10 (N=93) 60% No Desc 62% Not Appr

14% ID/Cust 5% Up to 10 Chicago FP—Only 25% 17% 7% Some Desc 12% Over 10 (N=42) 79% No Desc 83% Not Appr

31% ID/Cust 19% Up to 10 Evid 35% 37% 16% Some Desc 24% Over 10 (N=80) 53% No Desc 57% Not Appr

18% ID/Cust 16% Up to 10 No—Evid 24% 33% 18% Some Desc 5% Over 10 (N=1O3) 64% No Desc 79% Not Appr

12% ID/Cust 9% Up to 10 I Oakland FP—Only 29% 45% 15% Some Desc 9% Over 10 (N= 33) 73% No Desc 82% Not Appr I 56% ID/Cust 40% Up to 10 Ev I d 50% 49% 15% Some Desc 37% Over 10 (N= 43) 29% No Desc 23% Not Appr I

* The follow—up apprehension rates (over 10 mins) discussed on the previous page were computed after first removing the incidents I resulting in immediate apprehensions (up to 10 mins).

—172— tion variable can assume three levels: no description of the suspect;

some description (meaning anything from a general description (race or

sex or clothing) to actual naming of a suspect), and identified/in custody where the suspect was immediately taken into custody or else was named and placed. It is interesting to observe that evidence cases have

high rates of “ID/In Custody” while most no evidence and fingerprint—

only cases begin with neither a suspect in custody or named and placed.

The time to apprehension of suspects gives some indication of how

many cases are eventually solved where the suspect is not apprehended within ten minutes of the discovery of the crime. In cases that are not

solved immediately by apprehension of the suspects one might expect

those with physical evidence to be solved at a higher rate than those

with no physical evidence. In general this is found to be true. For

example, no evidence burglaries in Peoria result in an arrest in only 0 about 7% of the cases not solved immediately. For fingerprint—only

cases the percentage of cases not solved immediately (apprehensions made

within 10 minutes) which result in a follow—up arrest is 23%, while the

follow—up arrest rate for the evidence cases is 64%. The respective

rates for Chicago are 11%, 13%, and 30%, while for Oakland they are 6%,

10%, and 62%. (See footnote at bottom of Table VI—13 for explanation.) In Chicago, an interesting pattern emerges; the cases where only fingerprints are collected and examined are, in terms of other in vestigative information, inferior when compared with those where either

other kinds of evidence are examined, or even those where no evidence at

all is found. The fingerprint—only cases are responded to slower, and

have fewer witnesses and/or suspects than do the cases with no evidence

collected. Although the case sample is far too small to make any firm a —173 judgments, one plausible explanation emerges. The collection of fin gerprints in burglaries under the circumstances where information about suspects and witnesses is lacking can be classified as a true “longshot” attempt by investigators to identify a suspect.

These may also represent cases in which patrol officers and detec tives call evidence technicians to the scenes of crimes which will probably be suspended or closed but where the police officer wants to

“give the victim some service.” Such “service” may include a search for physical evidence even though the chances for a fingerprint identifica tion or match are extremely remote. It is not at all uncommon for technicians, in all of the jurisdictions, to be used as “public rela tions” officers and, in particular, not to disappoint crime victims who have grown to expect a search for physical evidence by virtue of watch ing police television programs where this is standard procedure.

The Role of Physical Evidence in Drug Cases

Several studies have noted the proliferation of drug evidence into forensic laboratories (Benson et al., 1970; Parker and Gurgin, 1972).

It is not unusual for more than 5O of all cases handled by a laboratory to be controlled substance related. Drug evidence is unique in that scientific analysis of the physical evidence (the questioned substance) is necessary to establish that a crime has been committed. Typically, a suspected user or dealer cannot be convicted of the crime until the laboratory has shown the substance he or she possessed is controlled by statute.

—174— for

may

the

call

but

cases

each

the

Kansas

and

This imme

two—

where

the

with

his/her

business of

the

street

tip,

“ID/In

incidents

the

statistics

one

the

Peoria

least

more jurisdiction cases

along or

City. such

drug

disturbance

custody is

premises.

only

on in

selected

place

from the

residence.

the

three

call,

only

informant’s

minor

Kansas

there

been descriptive

cases suspect in

one—third

locations.

person a

interesting

and

placed

filed

every 46

the

has to

the

City

represents

hand,

involvement,

private

markedly

while address

made

About

scene

90 a

stop

unrelated

cases

is (an

are

out other vary

which

several

Chicago

charges

Kansas

over

drugs

crime

response

suspect In

two

the

filed.

drug initiated

police

—175—

and

the warrant

convicted

70 offense

located a

the

Arrests

are

examination

reveals

in or

however,

case,

Oakland).

almost convicted,

An police

drug.

respond

and

drug

time

with cities.

cities,

about

found

discover

VI—14)

drug

cases.

charges Chicago,

the

being

perhaps,

of raid

four

offender

(89

police and

“street—outside” rate

of the

cities.

conviction,

approximately

for

suspected

the

represents

(Table

where

identified

figure

scene

when

high

police

cases

the

three

study

evidence

82’!.

filed. This

defendant

the

else

cases

the

violation,

This

than in

the

each

rates

scenario

the

occurs

are

four sample

from

disturbance,

five

percentage

Note

Often

The

those

discover

the

also

jurisdiction.

Peoria.

traffic

of for

characteristics.

typical

high and a

it Oakland vehicle. result family

diately

provided) Custody” thirds cases in to

charges

result

every

I TABLE VI—14

DRUG CASES (Descriptive Statistics)

Kansas Variable Response Peoria Chicago City Oakland (N=52) (N=53) (N=46) (N’73)

Who Initiated Police 63% 57% 63% 88% Report Other 37% 43% 37% 12%

Location Crime Street—Outside 62% 43% 59% 65% Committed Residential 21% 40% 25% 26% Non—Residential 17% 17% 16% 9%

Location Evid Suspect 96% 68% 69% 92% Collected Resid Scene 12% 32% 9% 4% Other 8% 8% 22% 4%

Results of Identification 86% 79% 94% 85% Lab Analysis Neg—Ident 12% 13% 4% 12% Other 2% 8% 2% 3%

Description of ID/Custody 92% 98% 82% 95% Susp at Search Some Desc 8% 2% 18% 5%

Apprehension Up to 10 Mins 54% 92% 78% 80% Time Over 10 Mins 35% 2% 13% 15% Not Apprehend 12% 6% 9% 5%

Clearance Rate 85% 92% 83% 97%

Incidents With an Arrest 88% 94% 91% 95%

Incidents With Charges Filed 73% 77% 67% 89%

Incidents With a Conviction 46% 15% 35% 26%

—176— drug

the

city

such

a rule

to the

Kansas

the

programs physical

sanctions

many

times

small

cases.

possible

getting

of conviction

charac

Department

police

cases,

conviction However, where

the

four

while

three

severe

attributed

convicted

exclusionary

also

counseling

absence

cases

dispositions

time.

be to

number more

Chicago

(Illinois

one

program,

and

plus

drug the

may the

due successful not

considerations,

the

those

find

the

substance,

variation

are

information

practically

attributable

areas

may

rates

only is

Oakland,

these

arson,

94%

wide

system,

may special

presence

79%

there

prosseci

record.

cases

In and

largely

common

the completes

supplying

controlled

still

Peoria

urbanized

—177— Beyond

and,

base, is

nolle

court

justice

such

for

is selecting

for

rape, conviction

in less

defendants

data

results.

when

defendants

identification

there

lost

crimes.

our

where

control official

criminal

successfully

conviction

difference

cases,

exchange

even

are

Arsons

homicide,

conviction

these

the

in crimes

other

identified

defendants

variation

of this local

and

positive

part

1983).

other

laboratory

cases

VI—15,

why

the unable

identified,

the

in phenomenon

about

divert

defendant

result rate

cases

similar

Rapes

drug

not

Some

appear

dismissed

the

Table

The

Chicago; city

will

for

cases

Some

not

there in

Although

Corrections,

large

City

explanations

charge. Although

charges

violations;

prosecutors courts

and,

will

differences

suspected

seen

City

substance

rates.

rate

teristics

issued —

Homicides,

evidence

U fl

S I

TABLE VI—15 I

CONVICTION RATES FOR DRUG CASES WITH LABORATORYIDENTIFICATION (N = Persons Charged) I I Kansas Peoria Chicago City Oakland (N=31) (N=31) (N=31) (N=54) I I Conviction Rate 65 23% 52% 31% a

—178— I

are are

of of

the the

The The

a a

arr— arr—

in in

prose— prose—

Kansas

cases cases

of of

also also

which which

and and

higher higher

greatest greatest

trial trial

result result

while while

in in a

filed

all all

is is

the

rape! rape!

charges charges

the the

for for

of of

It It

cases cases

are are

in in

by by

fraction fraction

convictions.

that that

motion motion

arrests arrests

Although Although

verdicts. verdicts.

cases cases

a a

homicide homicide

(l7), (l7),

in in

have have

9O. 9O.

of of

which which

nonetheless nonetheless

greatest greatest

of of

these these

filed filed

in in

trial trial

these these

is is

charges charges

respectively, respectively,

evident evident

tabulated tabulated

highest highest

of of

the the

fraction fraction

process. process.

Peoria Peoria

result result

through through

of of

Oakland Oakland

City City

and and

5l 5l

being being

the the

are are

also also

or or

the the

also also

in in

and and

which which

9O 9O

percentage percentage

respectively. respectively.

and and

percentage percentage has

in in

are are

Approximately Approximately

are are

Kansas Kansas

the the

laboratory laboratory

judicial judicial

judge judge

guilty; guilty;

percentage percentage

trial trial

charges charges 58h

cases, cases,

charges charges

these, these,

in in

convictions. convictions.

Chicago Chicago

of of

the the

downgrading downgrading

the the

to to

in in

cases cases

Peoria Peoria

—179— —179—

the the

of of

highest highest

in in

go go

VI—l7). VI—l7).

these these

and and

trial, trial,

the the

these these

cases cases

the the

processing processing

acquittals acquittals

pleas pleas

describes describes

convictions, convictions,

and, and,

of of

to to

of of

result result

(5l). (5l).

prosecutor, prosecutor,

results. results.

in in

cases cases result

Oakland. Oakland.

Table Table

has has

and and

levels levels

go go

case case

addresses addresses

and, and,

outcome outcome

examined examined

(78) (78)

in in

the the

(54) (54)

the the

rates rates

of of

plea plea

homicide homicide

(see (see

(VI—l6), (VI—l6),

is is

cases cases

that that

by by

the the

of of

result result

evidence evidence

dismissed; dismissed;

the the

Oakland Oakland

filed filed

of of

pleas pleas

trial trial half

section section

laboratory laboratory

screening screening

74 74

of of

guilty guilty

table table

cases cases

to to

convictions convictions

are are

Disposition Disposition

patterns patterns

a a

being being

than than

dismissal dismissal

offenses offenses

examine examine for

evidence evidence

This This

(92) (92)

of of and

go go

of of

guilty guilty

in in

physical physical

dismissed dismissed

first first

to to

percentage percentage

The The

counsel. counsel.

various various

in in

69 69

More More

that

are are

charges charges

where where

Sir’ilar Sir’ilar

with with

charges charges

One—third One—third

The The

Rates Rates

these, these,

smaller smaller

percentage percentage

cutor. cutor.

result result

ests ests

sex—related sex—related percentage

cases cases City.

filed filed

resulting resulting

defense defense

in: in:

percentage percentage verdicts.

which which

controlling controlling

teresting. teresting. survive

possible possible

cases cases U U I I I I I 1 I I

14%

81%

11% 51% 41%

89%

N=63

trial,

Oakland

are

stand still

City

is to

85% 33%

18%

35%

71%

29%

N47

WHICH

defendants

Kansas

ANALYZED

where defendant

63% 20%

35%

46%

76% 24% incompetent

CASES

N=73

Jurisdiction

Arrested) Chicago

the

VI—16

cases

—180—

found

few

TABLE where

EVIDENCE

HOMICIDE

Persons

15%

82%

78%

10%

90% those

Peoria

N33

offenses,

died,

PHYSICAL

OUTCOME

other

includes

community.

for

defendant

the

Filed

the

Plea

category

Terminations*

Convicted

Acquitted

Cases

large

This prosecuted

where

Disposition

Charges

Dismissed Other

Guilty

Trial

8% 8%

17%

92% 92%

54%

29%

89%

N=79 N=79

Oakland Oakland

City City

22% 22%

78% 78%

19% 19%

29% 29%

52% 52%

86% 86%

N=36 N=36

Kansas Kansas

ANALYZED ANALYZED

OFFENSES OFFENSES

IS IS

Jurisdiction Jurisdiction

31% 31%

69% 69%

15% 15% 58%

27% 27%

91% 91%

N66 N66

Chicago Chicago

Arrested) Arrested)

VI—17 VI—17

—181— —181—

EVIDENCE EVIDENCE

TABLE TABLE

Persons Persons

RAPE/SEX-RELATED RAPE/SEX-RELATED

26% 26%

74% 74%

24% 24% 51%

24% 24%

95% 95%

N=39 N=39

Peoria Peoria

PHYSICAL PHYSICAL

OF OF

(N (N

WHICH WHICH

OUTCOME OUTCOME

IN IN

Plea Plea

Convicted Convicted

Acquitted Acquitted

Trial Trial

Guilty Guilty

Dismissed Dismissed

Charged Charged

Disposition Disposition

0 0

I I

I I 0 0 I

but

the

are

The

City.

other

hom

trial

been

cases

labo

cases

Chicago

with

all

rates analyzed

however.

present

and

City.

Kansas

have

for

the

in two—thirds

cases laboratory

rapes,

City,

cases

pleas

against

comparison.

Kansas

where

results

into

forty—three a

arrested

cases

where

Outcome

Kansas

and significant,

acquittals).

the controlling

(guilty Chicago

charges

were

suspected

and

others. cases

.01)

permit

contrasted

and

the

judicial

separated

to was

Judicial

all

filed

percent of

are with (p

jurisdictions

Chicago

and

been

semen

cases

conviction,

Chicago

statistically

convictions

individuals

—182—

VI—l8).

versus These

only

eighty

(dismissals

have

Oakland

not

discussion,

combined

about

where

the

prosecutor and

Results

Table

are

rates

only

this

results

The

origin.

sampled

are

results

(see

of categories,

fire—related jurisdictions,

City

Chicago

City, general,

incidents

two

the

City. obtained

Laboratory

nonconvictions

common

displays

cases

identified

a of

Kansas

laboratory

incidents

different

into

purposes

and

Kansas

were

laboratory

number

cases in

City

two

VI—19

Kansas

the

showed

detected.

origin

principally

results.

semen

Only

Homicides:

For

Table

arrest

Kansas

not

sufficient thirty—eight

reviewed

the

and

the

Convictions

consolidated

icides, convictions)

common

results where

cases,

was

ratory

substantially

differences City

5O 25

25%

N=1O

100%

Kansas

WHICH

ANALYZED Jurisdiction

arrested)

VI—18

OFFENSES

67 —183—

42 17%

Chicago N=18

100%

TABLE

EVIDENCE

Persons ARSON =

PHYSICAL

OUTCOME

Plea

Convicted

Acquitted

Disposition

Charged

Dismissed

Guilty

Trial

ft I

4 0

I I I U I U I ft I

TABLE VI-19

RATES OF CONVICTION FOR PERSONS ARRESTED FOR MURDER, CONTROLLING FOR LABORATORYRESULTS (N Persons Arrested)

Jurisdiction Laboratory Results Peoria Chicago Kansas City Oakland (N = 33) (N = 74) (N = 47) (N = 63)

No Common 63 40% 17% 48% I Origin (8) (48) (6) (29)

* *

Common Origin 52% 50% 44% 82% (25) (26) (41) (34)

** Chi Square Significance p < .01. 1

—184-

a a

the the and

when when

does

has has

knew knew Kansas

victim

and and

be be

was was

result.

juris

can can

In In

robbery, robbery,

greater

the the

to to

seminal seminal

as as

victim victim

she she a

all all

in in

between between victim

result result

commonly commonly

Chicago Chicago

evidence evidence

in in

a a

clearance, clearance,

the the

has has

where where

found. found.

twelve—fold twelve—fold

the the

that that

appear appear

are are

or or

finding finding

laboratory laboratory

and and

not not

contact contact

rapes rapes

where where

cases cases

suspect

of of

higher higher

reduction reduction

where where

would would

is is

physical physical

states states

convictions, convictions,

semen semen

in in

increase increase

the the

origin origin

are are

arrest arrest

of of

sexual sexual

and and

Outcome Outcome

cases cases

is, is,

impact impact

charge charge

of of

significant. significant.

semen semen

significant significant

stranger

Chicago, Chicago,

in in

without without

gaining gaining

the the

common common

and and

In In

to to

not not

That That

are are

irrelevant.

victim victim

in in

a a

rates rates

and and

showing showing

where where

of of

relationship relationship

Judica]. Judica].

conviction conviction

does does

assailant, assailant,

conviction conviction

—185— —185—

are are

be be

in in

the the

it it

of of

and and

with with

to to

the the

cases cases

results results

identification identification

and/or and/or

stranger stranger

Chicago. Chicago.

because because with

bargaining bargaining

than than

odds odds

evidence evidence

evidence. evidence.

important important

in in

the the

with with

rates rates

cases cases

with with

prove prove

and and

semen semen

be be

Results Results

the the

of of

plea plea

differences differences

Here Here

The The

differences differences

rates rates

may may

to to

victim/suspect victim/suspect

semen semen

where where

laboratory laboratory

the the

of of

Peoria Peoria

for for

compared compared

involvement involvement

convictions convictions

associated associated

associative associative

there there

the the

in in

victim

VI—20. VI—20.

appear appear

.05).

cities cities

Laboratory Laboratory

strangers, strangers, rape rape

< <

conviction, conviction,

examination examination

conviction conviction

and and

substantial substantial

found, found,

finding finding

Oakland, Oakland,

sexual sexual

other other

where where

(p (p

are are

in in

participant. participant.

only only

Table Table

rapes, rapes,

on on

origin origin

is is

or or

This This

and and

The The

in in

In In

Controlling Controlling

Rapes: Rapes:

defendant defendant

deny deny

previously previously

the the

charging, charging,

revealed revealed

semen semen Summary

the the

suspect suspect

effect effect City

fluid fluid

defendant defendant

crucial crucial willing

not not

was was

seen seen dictions Oakland

common common But

fl fl

I I

b b A A TABLE VI—20

RATES OF CONVICTION FOR PERSONS ARRESTED FOR RAPE, CONTROLLING FOR LABORATORYRESULTS

(N = Persons Arrested)

Jurisdiction Laboratory

Results Peoria Chicago Kansas City Oakland (N = 39) (N = 66) (N 37) (N 79) a I Negative I.D.! 45 23% 22% 44% No Common Origin (20) (13) (9) (36)

* *

Semen I.D.’ed/ 68% 66% 39% 67% I Common Origin (19) (53) (28) (43)

* Chi Square Significance p < .05 j

—186—

that

of of

In In

as as

in in

at at

evi evi

physi

physi— physi—

likely

evidence evidence

more more

convic convic

physical physical

no no

results.

cases cases

the the

in in

variables: variables:

controlled controlled

are

result result

with with

more more

and and

with with

incorporated

fail fail

reverse reverse

cleared cleared

police. police.

be be

than than

evidence.

categories categories

without without

plea.

are are

physical physical

dispositions dispositions

cases cases

are are

the the

result result

the the

significant significant

are are

between between

cases cases

the the

results results

this this

rate rate

laboratory laboratory

do do

evidence evidence

following following

cases cases

cannot cannot

results results

but but

of) of)

In In

evidence evidence

cases cases guilty

of of

cities. cities.

investigation; investigation;

a a

without without

the the

testing testing various

than than

elapsed elapsed

than than

the the

origin origin

evidence evidence

higher higher

evidence evidence

an an

where where

without without

these these

four four a

for for

the the

types types

physical physical

of of

evidence evidence

(arrival (arrival cases

without, without,

time time

particular, particular,

at at

traditionally traditionally

through

the the

level, level,

offenses. offenses.

common common

cases cases

to to

in in

success success

with with

and and

other other

reduction reduction

of of

physical physical

laboratory laboratory

in in

in in those

outset outset

than than

scenes; scenes;

—187— —187—

trial trial

other other

However, However,

physical physical

of of

or or

with with

to to

cases cases

report report

the the with

with with

controlling controlling

than than

three three

crimes, crimes,

greater greater

of of

charge charge

such such

clearance clearance

involving involving

trial trial

go go

at at

emerges emerges

in in

its its

jurisdictions, jurisdictions,

at at

cases cases

to to

rate rate

cases cases

while while

with with

arsons. arsons.

results results

often often more

information; information;

victims victims

cities, cities,

and and

where where

cases cases

jurisdictions.

of of police

trend trend

absence absence

are are

four four

the the

rates rates

burglary/property burglary/property

and and

the the

tend

suspect suspect

a a

the the

more more

or or

two two

with with

level, level,

higher higher

the the

a a

the the

cases cases

crime crime

and and

than than

of of

a a

examined examined

witness witness

When When

of of

At At

rapes rapes

cities, cities,

of of

in in

higher higher

adjudicated adjudicated

at at

the the

absent, absent,

of of

disposed disposed

other other

two two

court court

are are

burglary/property burglary/property

evidence

the

be be

substantially

is is

of of

presence presence

analysis, analysis,

In In

even even

are are

offenders offenders

three three

the the

and and

to to

of of

in in

pleas pleas

dismissed dismissed

with with

cases cases

The The

the the

in in

In In

significantly significantly

At At

evidence. evidence.

two two

homicides, homicides,

be be

not. not.

in in

likely likely

In In

to to

into into

sociate sociate

true true

result result

cal cal

tion tion

do do

guilty guilty

formation formation

significantly significantly Cases

identification identification

discovery discovery general,

availability availability

cal cal

dence dence

robbery robbery

evidence evidence

assault/battery, assault/battery, fl fl such cases where physical evidence was examined have been compared controlling for laboratory results. Rates of conviction in homicide cases with common origin laboratory results are substantially higher in two jurisdictions, Kansas City and Oakland, but are statistically sig nificant in only one, Oakland. In rape cases, the identification of semen proved to be significantly associated with conviction in two jurisdictions: Chicago and Oakland.

—188—

of of

as as

by by

the

For For

type type

for for from no

arises

witness

and and

time time

State

Gilliland, Gilliland,

effects effects

analysis analysis

and and

levels. levels.

accomplished accomplished

* *

CLEARANCE CLEARANCE

witnesses, witnesses,

question question

controlling controlling

Dennis Dennis

evidence evidence

elapsed elapsed

was was

ON ON

A A

Michigan Michigan

suspect suspect

marginal marginal

Dr. Dr.

the the

log—linear log—linear

at at

while while

ANALYSIS ANALYSIS

for for

specified specified

the the

of of

for for

response, response,

the the

at at

analysis analysis

suspect, suspect,

EVIDENCE EVIDENCE

chapter. chapter.

VI—2 VI—2

or or

a a

an an

VII VII

with with

rates rates

of of

misleading.

conviction conviction

LOG—LINEAR LOG—LINEAR

—189— —189—

Probability Probability

Table

assistance assistance

report report

PHYSICAL PHYSICAL

be be

investigated investigated variables

in in

previous previous

and and

chapter. chapter.

and and

OF OF

CHAPTER CHAPTER

the the

to to

we we

USING USING

Typically, Typically,

the the

knowledge knowledge

assistance assistance

conviction conviction

police police

this this

in in

control control

as as

control control

to to

of of

his his

and and

EFFECTS EFFECTS

results results

clearance clearance

chapter chapter

of of

the the

Statistics Statistics

VJ—2 VJ—2

for for

on on

THE THE

CONVICTION CONVICTION

acknowledge acknowledge

the the

crime crime

of of

factors factors

lack lack

with with

to to

writing writing

AND AND

Table Table

the the jurisdiction.

clearance clearance

previous previous

the the

such such

the the

causes causes

of of

wish wish

see see

cases cases

and and

evidence evidence

of of

the the

ESTIMATING ESTIMATING

and and

University, University,

Professor Professor

We We

In In

* *

whether whether

to to

example, example,

evidence evidence ___

calculating calculating variables

offense, offense,

effects effects discovery

Introduction Introduction

physical physical U U In this chapter the results of a more sophisticated (log—linear) analysis of the data are reported using Everyman’s Contingency Table Analysis (ECTA)* to quantify and model the simultaneous joint effects of several independent variables or factors on selected dependent or re sponse variables. Each of the three models presented includes physical evidence as one of the independent variables and clearance or conviction as a dependent variable. The advantage of this approach is that in teractions and differential effects of evidence on the response variable that might otherwise go undetected can be estimated. Also it allows for the fitting of various models to the data for the purpose of testing various theories on the effect of evidence. Because of the relatively small sample sizes for the number of independent variables examined, the data analysis and model fitting

* Everyman’s Contingency Table Analysis (ECTA) is a computer program developed to carry out the log—linear analysis developed by Goodman and Fay (1973).

—190— is largely descriptive in nature. (Statistical results which depend on large sample sizes, such as the estimates of standard deviations of lambda effects, are discounted.) However, these results are illuminat— ing and provide interesting sample descriptions of the effect of evi

dence on clearance and convictions along wit-h the interaction of evi—

dence with other factors. Terms such as “impact” and “effect’ may be used in this chapter in discussing what is more properly called “association”.

remainder of this chapter is divided into two sections, the The first addressing the effect of evidence on clearance and the second the

effect of evidence on conviction. All variables employed in the

analyses are defined (see Tables Vu—i and VII—4) in this chapter. The

tables which display the raw frquencies used in the analysis are in— cluded in Appendix 0.

The Effects of Physical Evidence on Clearance

first model discussed employs CLEARANCE as the response or depend The ent variable. The independent variables included in the analysis are:

a) EVIDENCE — The presence or absence or scientifically examined physical evidence is controlled in accord— ance with the sampling procedures discussed in U Chapter VI.

b) TINE — This variable fundamentally measures the speed with which offenses are reported to! responded to by the police: either 10 minutes or less, or greater than 10 minutes.

c) WITNESS—SUSPECT — Originally WITNESS and SUSPECT were to have been treated as two separate variables, basically corresponding to the presence or absence of witnesses and suspects at the preliminary investigation level. However, insufficient data are available for the combination where witnesses are absent yet suspects are in custody or named • and placed. For this reason a single, three—level composite variable has been created. —191— if

I I I

I I

for for

VII1 VII1

given given

where where

a a

these these

the the

each each

these these

Appendix Appendix

Table

the the

to to

cases cases

and and

which

in in

the the

frequencies frequencies

cases, cases,

type: type:

by by

levels. levels.

in in

chapter chapter

raw raw

refers refers

those those

of of

class class

product product

robberies; robberies;

D—2 D—2

cells cells

1,650

summary summary

is is

estimating estimating

primarily primarily

the the

yariable, yariable,

various various

for for

described described

a a

offense offense

The The

of of

clearance clearance

in in

it it

composed composed

batteries; batteries;

288 288

simple simple

miscellaneous miscellaneous

all all

the the

number number

previous previous

by by Table

variable variable

for for

robbery robbery

= =

jurisdiction jurisdiction

unarmed unarmed

combinations combinations

in in

type type

that that

the the

and and

the the

contains contains

See See

response response

give give

The The

each each

J J

consist consist

for for

and and

clearance clearance

(4) (4)

variables variables

VII—l VII—l

in in

VI, VI,

the the

variable. variable.

0 0

aggravated aggravated

(3) (3)

—192— —192—

principally principally for

table): table):

the the

offense offense present

classified classified

is is

W W

armed armed

(3) (3)

possible possible

Table Table

differences differences

is is

percentage percentage

levels. levels.

and

Appendix Appendix

beneath beneath

notations notations

the the

T T

analysis analysis all

are are

for for

Chapter Chapter

are are odds

(2) (2)

analyses analyses

demonstrated demonstrated

burglary. burglary.

the the

to to

both both

the the

E E

of of

controlling controlling

necessary. necessary.

In In

(2) (2)

for for

the the

classification classification

small small major

or or

particular particular

4 4

The The

all all

C C

is is

so so

rates rates

evidence. evidence.

a a

cases cases

(2) (2) in in

— —

assaults assaults

control control

(CLEARANCE) (CLEARANCE)

specified specified

that that

of of

categories categories

that that

D—2 D—2

and and analyses

empirical empirical

All All

C C

parentheses parentheses

referred referred

to to

includes includes

at at

column column

crimes. crimes. assault assault

— —

of of

corresponding corresponding

origin origin

burglary burglary

and and

in in

is is

the the

in in

are are

classified. classified.

employed employed

showed showed

represents represents

conviction conviction

effects effects

the the

assault assault

D—l D—l

case case

aggravated aggravated

be be

their their

cells. cells.

levels levels

number number

cross—classified cross—classified

data data

reader reader

of of

jurisdictions, jurisdictions,

JURISDICTION JURISDICTION

the the

and and

also also

ification ification

the the

property property necessary necessary

and and bi—variate

of of burglaries

robbery, robbery,

OFFENSE OFFENSE

(288) (288)

(Levels) (Levels)

provide provide

of of

288 288

is is

(Variables) (Variables)

could could Tables Tables

The The

notations notations

The The

e) e)

d) d)

variables variables

the the

tables tables

these these

levels levels

case case

(see (see

number number

which which variables, variables, TABLE Vu-i

VARIABLES FCR LOG—LINEAR ANALYSIS USING CLEARANCE AS THE DEPENDENT VARIABLE U VARIABLE NUMBER NUMBER VARIABLE TYPE NOTATION OF LEVELS LEVELS

1 Clearance Response C 2 1= Cleared 2 Not Cleared

I 2 Evidence Factor E 2 l No Evidence 2= Evidence B 3 Time Factor T 2 1= Response 10+ minutes 2= Response 10— minutes

3* 4 Witness—Suspect Factor W 1 No Witness & No Suspect 2= Witness & No Suspect 3= Witness & Suspect

5 Offense Factor 0 3 1= Robbery 2= Assault I 3 Burglary

6 Jurisdiction Factor J 4 1= Peoria B 2= Chicago 3 Kansas City 5 4 Oakland

* Originally Witness and Suspect were to have been treated as separate factors with each at two levels. No data are available in the No Witness—Suspect combination so the single composite variable has been created.

—193— where the empirical odds for clearance in Peoria (J1) assault (0=2) cases are 12/2 (12 cleared, 2 not cleared) where there is at least one witness but no suspects (W2), the case has physical evidence (E=2) and the elapsed reporting time to the police is 10 minutes or less (T2).

Appendix D contains further aggregations of these clearance odds across offense categories and across jurisdictions (see Appendix, Tables D—4 and D—5).

First of all, the log—linear analysis tests the independence of C

(CLEARANCE) and E (EVIDENCE) and finds that they are not independent, while controlling for the other variables. This analysis also deter mines that considerable variation in odds for clearance is explained by

EVIDENCE, in addition to variations explained by the other factors

(TIME, WITNESS, OFFENSE and JURISDICTION). The next objective is to find a simple model that fits the data well so that the relationship between CLEARANCE and EVIDENCE can be quantified.

A rough quantification of the effects of the different variables on

CLEARANCE is made possible by a preliminary additive model. Table VII—2 presents the estimated increase in odds for clearance attributable to each variable individually, while controlling for the effects of all the other variables. The WITNESS variable clearly has the greatest effect on clearance. Moving from Level 1, where there are neither suspects nor witnesses identified at the preliminary investigation, to Level 3, where there are both witnesses and suspects, demonstrates the increase in the odds for clearance by a factor of almost 28. The EVIDENCE variable is associated with a three fold increase in odds for clearance by moving from the no—evidence level to the evidence level. This increase in odds is comparable to the increase which results when the WITNESS variable

—194— in .58 (no 7.73 1.77 1.02 3.61 3.12 1.63 Odds 27.90 1 Increase levels. Level suspect). and and from Y Y moved From variables witness 3* 3 2 2 2 3 3 2 VARIABLES Clearance Level of has CLEARANCE Level in OF (both VII—2 to Moving on 3 X X —195— By 1 0 1 1 1 2 1 1 2 variable TABLE EFFECTS Level W Level Odds Level description Improvement to a T witness E for ADDITIVE the suspect) VII—l case Table this In See witness/no * Variable WITNESS EVIDENCE OFFENSE TIME

I I

10 10

the

odds odds

when when

of of

EVI EVI

WIT WIT

on on

10 10

on on

suspect -

of of

time time

WITNESS, WITNESS,

was was

witness.

no no

factors factors

levels levels

simplest

increase increase

effect

CLEARANCE CLEARANCE

one one

exceeds exceeds

of of

factors factors

EVIDENCE EVIDENCE

with

model model

The The

effects effects

VII—3. VII—3.

other other

response response

for

The The

for

levels levels

time time

least

the the

direct direct

this

other other

the the

a a

Table

the the

at at

odds odds

odds” odds”

not. not.

how how

the the effect

situation situation

in in

See See

with with

has

a a

combinations combinations

where where

included.* included.*

of of

with with

response response

the the

it it

unless unless

36 36

describing describing

TIME TIME greater

are are

from from

but but

the the

is, is,

Cases Cases

when when

levels levels

interact interact

that that

—196— —196—

“increase “increase

times times

That That

going

where where

3x3x4 3x3x4

discussion discussion

the the

VII—l) VII—l)

over over not

an an

variable variable

adequately adequately suspect, suspect,

——

1.5 1.5

JURISDICTION. JURISDICTION.

is: is:

the the

2 2

full full

reveals reveals

upon upon

no no

the the

does does

clearance. clearance.

(Table (Table

and and

of of

a a

have have

well well

offenses offenses

reveals

on on

and and

Level Level

with with

that that

available

for for

each each

explained explained

less less

data data D

testing testing

to to

depends depends

than than

is is

JURISDICTION. JURISDICTION.

one one

OFFENSE OFFENSE

model model

be be

or or

for for

effect effect

found found

the the

to to

ETWOJ/CEWO/CEWJ/CT ETWOJ/CEWO/CEWJ/CT

and and

clearance clearance

JURISDICTION JURISDICTION

its its

was was

fit fit

Level Level

cannot cannot

rigorous rigorous Appendix

evidence evidence

CLEARANCE CLEARANCE

in in

for for

It It

clearance clearance

evident evident

minutes minutes

WITNESS, WITNESS, minutes.

and and

witness witness

that that

derived). derived).

from from on

OFFENSE OFFENSE

(See (See

(Ml) (Ml)

is is interactive interactive

* * More More

______

no no

factors factors

odds odds

This This physical

CLEARANCE CLEARANCE OFFENSE

model model

and and NESS,

DENCE DENCE moves moves The value 5.13 (first column, first row) may be interpreted as the estimated increase in odds for clearance for having physical evidence over having no physical evidence when there are no witnesses and no suspects for robberies in Peoria. In other words, robbery offenses in Peoria with physical evidence, but where no witnesses or suspects are in custody or named and placed, are five times as likely to be cleared as similar robbery offenses without physical evidence. The .99 value in column one, row two shows that assault cases with no immediate suspects or witnesses have virtually the same odds for clearance where evidence is present as where it is absent. Peoria and Oakland show very similar results. Evidence has its greatest association with clearance in these jurisdictions followed by

Kansas City and, then, Chicago. Where there are no suspects in custody or named and placed at the preliminary investigation, physical evidence has its greatest association with clearance for burglary, and, to a lesser degree, for robbery. Little effect is evident on assault. With a suspect present, evidence has its greatest association with clearance for the crime of assault. On an offense by offense basis, the following conclusions can be drawn:

Robbery — In all jurisdictions, except for Chicago, physical evi dence has its greatest effect when there are no witnesses and there are no suspects. The victim of a robbery is considered to be a witness if he/she provides information to the police about the offender, e.g., a description of the suspect or the crime. There are very few cases with no witnesses and no suspects in the sample. Therefore, we focus on the second level where a witness is identified, yet there is no suspect. In

—198—

4.29 4.29

1.59 1.59

8.56 8.56

6.07 6.07

1.06 1.06

8.34 8.34

5.45 5.45

19.43 19.43

17.71 17.71

Oakland Oakland

.39 .39

.84 .84

City City

Kan

1.06 1.06

2.12 2.12

2.68 2.68

2.45 2.45

2.38 2.38

2.41 2.41

3.67 3.67

Clearance Clearance

Jurisdiction Jurisdiction

.33 .33

.96 .96

.18 .18

.92 .92

3.29 3.29 1.22 1.22

6.57 6.57

1.05 1.05

1.41 1.41

for for

Chicago Chicago

Odds Odds

.99 .99

3.40 3.40

1.26 1.26

6.77 6.77

5.95 5.95

7.86 7.86

5.13 5.13

on on

19.04 19.04

17.36 17.36

Peoria Peoria

(NI) (NI)

VII—3 VII—3

Model Model

Evidence Evidence

TABLE TABLE

for for

of of

Burglary Burglary

Robbery Robbery

Assault Assault

Burglary Burglary

Assault Assault

Robbery Robbery

Burglary Burglary

Robbery Robbery Assault

Offense Offense

Effect Effect

Suspect Suspect

No No

Estimated Estimated

Suspect Suspect

No No

Witness; Witness;

Variable Variable

Witness; Witness;

No No

Witness—Suspect

a a

I I

I I I

I I

i i

I I

I I I I and

are

dif

there witnes

offense

The

the

in—

routinely

helpful

cases

gathered see,

Peoria

physical

which exception,

clearance

for

odds

both

this

the

where

not

We make

jurisdiction

the

for

The

these

are of

odds

cases

are

witness placed. clearance

evidence

the

or odds

suspects

clearance.

being

cases.

for

there

evidence

Chicago,

seems

outset

present.

examined City,

when

for

nor

present.

evidence,

City

odds

presence represent

the

when

types

when solve

are

increase is

odds

to bloodstains,

the

evidence

Kansas

impact identified

less

increase

have

Kansas

assault

evidence

the

impact

and

course,

witnesses

physical

hard

that

the

suspects

much

where

evidence

custody

eightfold

—199—

Chicago,

such

greatest

and Oakland

are

terminated.

firearms

where

neither

greatest Without

firearms

cases

immediately

effect where

its

and

These,

clearing

suggests

are

the

are

jurisdictions,

closing

has

for

City.

This

jurisdiction

there

higher witnesses

clear.

suspects,

Chicago, Peoria

have

111—3).

there

assaults,

three to

odds

to identified

suspended

and

only

incidence

problematic

both significant

not.

suspects times

Kansas In

Evidence

when

The

Table

no —

these

the

— this

in no

however,

suspects

investigation.

when

these

even has

appears

(see

highest

but

suspects

difficult

that

witnesses

City,

configuration,

seventeen

double

Assault probably

when

the

and

Burgly

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locating

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than

than evidence

evidence

ses

are than

vestigation. in

collected

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ference

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exception

clearance

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preliminary

would

are

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been

(E=2);

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labo labo

should

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selected selected

mind mind

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variable variable

controls

have have

DISPOSI DISPOSI

where

well well

arrest arrest

in in

evidence evidence

origin origin

does does

as as

were were

evidence evidence

EVIDENCE EVIDENCE

reported. reported.

category category

and and

effects effects

incorporating

which which

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the the

location location

independent independent

a a

results results

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are are

base base

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of of

keeping keeping

common common

or or

incidents incidents

(E1); (E1);

(D=l) (D=l)

in in

analysis. analysis.

added added

three—tiered three—tiered

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the the

one one

data data

other other

variables variables

664 664

case. case.

the the

was was

evidence/no evidence/no

fall fall while

concerning concerning

this this

that

testing testing victim

analyses analyses

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than than

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clearance.

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evidence evidence

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does does

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conviction conviction

for for

at at

the the

be be

no no

used used

with with

variable variable

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research, research,

in in

Conviction

forensic forensic

—200— —200—

can can

odds odds

clearance, clearance,

only only

result result

laboratory laboratory

log—linear log—linear

information information

conviction conviction

variable, variable,

and and

on on

of of

presented presented

composed composed

we we

on on

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to to

analysis. analysis.

levels: levels:

fall fall

of of

court court

offender offender

is is

variables variables

RELATION RELATION

with with

disposition disposition

other other

the the

looked looked

not not

testing. testing.

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since since

arrest arrest

three three

the the

separate separate

in in

new new

EVIDENCE EVIDENCE

measure measure

base base

Evidence Evidence

recent recent

laboratory laboratory

results results

A A

final final

does does

hypothesis hypothesis

two two

has has

of of

the the

links links

rich rich

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section section

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data data

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combinations combinations

relationship relationship

the the

to to

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levels: levels:

defines defines

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association association precise

included included

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size. size.

laboratory laboratory

result result

to to

the the Physical Physical

its its

which which

this this

review review

two two

where where

section section

of of

factor factor

made. made.

(D2). (D2).

a a

in in

more more

VII—4 VII—4

VII—3 VII—3

therefore, therefore,

and and

were were

previous previous

(E3) (E3)

a a

prior prior

has has

sample sample

addition addition

this this

are are

and and

stronger stronger

result result

the the

upon upon

(D) (D)

In In

a a

In In

Table Table

analysis, analysis,

Table Table

laboratory laboratory

results results

evidence evidence

Effects Effects

limitations limitations

overall overall

the the

category category

ratory ratory

based based

the the dichotomy

introduced introduced provides

and and have variables

reported reported While

conviction conviction

variable, variable,

each each arrests TION

factors factors The The TABLE VII—4

VARIABLES j’OR LOG—LINEAR ANALYSES USING CONVICTION AS THE DEPENDENT VARIABLE

VARIABLE NUMBER NUMBER VARIABLE TYPE NOTATION OF LEVELS LEVELS

D Disposition Response D 2 1 No Conviction 2= Conviction

E Evidence Factor E 3 1= No Evidence I 2= Evidence and No C.O. 3 Evidence and C.O. *

R Relation Factor R 2 1= Suspect: Family! Friend 2= Suspect: Stranger

U T Time Factor T 2 1= Arrest 10+ mm. 2= Arrest 10— mm. U W Witness Factor W 2 1 No Witness 2= Witness a 0 Offense Factor 0 3 1= Robbery 2= Assault I 3 Burglary

J Jurisdiction Factor J 4 1= Peoria 2= Chicago 3 Kansas City 4 Oakland

U * Lab analysis of evidence resulted in a statement of common origin

B I

—201— II

time

the

only

report

because

they

OFFENSE

INSLAW

con

levels:

the

time

evidence

and

evidence

separate

less.

1977). crime

from

to by

studies

since

be The

victim—

two

shorter

prior

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either

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support

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and

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has

variable

victim

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inclusion

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elapsed

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likelihood

have

where

effects

analysis

after

conducted

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number

effects

minutes

and

for used

i.e.,

the

witnesses.

time

relationship

the

10 enough

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and

R2,

the

variable

jurisdiction

important

1977 no

victim

EVIDENCE

those

witnesses

minutes

and

jurisdiction

from

Research

large

simultaneously,

had

arrest; TIME

the

10 of

greater

the

be made

suspect

unknown.

(Vera,

considered

measuring

examining

The

and

offense,

examining

the

same

than

given

the

made.

—202—

sample

nearly

dropped

another;

offense,

for

absence

one,

the

variables

this

victim—defendant

other,

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not

outcome

one more

for

arrest

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interest

the

are

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between

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shown

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arrest made

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relationship

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cases

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shown

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presence

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performed:

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are

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sample

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664

This

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model.

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crime

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JURISDICTION

strangers

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(Forst

log—linear

suspect

conviction on arrest.

trolled.

lapse analyses

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occurred;

CLEARANCE

important

explaining arrest

T=l,

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model,

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relationship

are dichotomized: An to its of the among fourth to EVI ac one Appen greater great in of the OFFENSE presents acquain— a not in the 1.66 evidence 1.6 into contingency from or for in likely elapsed. no both has them between VII—5 OFFENSE as have in analyses. interactions have with taking J approximation family moving and produce finds conviction 0 Table independence twice by finding demonstrates to T —— offense TIME controlling for alternately rough E are minutes arrests without a D relationship also of maintained the friends, origin odds used ten and of than the well are variable, two—at—a—time J conditional aggregated CONVICTION. CONVICTION TIME 0 provides strangers common after of analysis each on R —— when involving a RELATIONSHIP, —203— importance then and E minutes empirical The for D in test made explained variables model conviction included: data show: the are ten a with raw those a be the odds involving the variable are variables those to three the data RELATION are for in of models within another. additive resulting as cannot models, raw See than with Crimes fit interacts these one leading made response demonstrated The D—lO), variables simple different prior the of increase EROJ/DEO/DEJ/DOJ for the and of evidence in models, the model D—8. conviction CONVICTION EVIDENCE CONVICTION. position. preliminary another. conviction Arrests and fairly a in odds (D—9 with on to and how The to for (M2) As Two JURISDICTION, prior Table estimated effects independent independent our subsequent and tables dix the the variable level lead tances. odds arrest collected. greater improvement EVIDENCE the be count effect DENCE

a a

is is

for for

are are

VII—6 VII—6 where

rob rob

physi

bur

for

pos

effect

JURIS

of of

evidence evidence

In In

no no

convic convic

were

determine determine and

is is

laboratory laboratory

though, though,

(J) (J)

odds odds

Tables Tables

to to

it it

for for

little little

in in

conviction conviction

conviction, where

conviction conviction

situations situations

conviction conviction

and and

models models

without without

origin origin

assault assault

result. result.

odds odds

in in for

has has

for for

model model

for for

categories categories

for for

unable unable

cases cases

factor. factor.

in in

Assault, Assault,

these these

is is

cases cases

odds odds

this

odds odds

OFFENSE OFFENSE

odds odds

result result in in

with with

poorer poorer

how how

improvement improvement

in in

but but

in in

(0) (0)

the the

offense offense

noncommon noncommon

on on

laboratory laboratory concerning concerning

—

a a

evidence evidence

Using Using

than than

Chicago. Chicago.

the the the the

—

differences differences

both both

results results

the the

Chicago.

in in from

and and

actually actually general

Peoria Peoria

of of

laboratory laboratory

in in

a a

of of

evidence evidence

the the

—204—

contrasts contrasts

evidence evidence

levels. levels.

with with

in in

improvement improvement

are are

improvement improvement

of of

discussion discussion

see see

than than

question question

moving moving

Oakland Oakland

CONVICTION. CONVICTION.

the the

true true origin

levels levels

three three which we

laboratory laboratory

in in

display display

full full

pronounced pronounced

(D) (D)

is is

regardless regardless

interact interact physical

a a

its its

effects effects

extent extent

estimated estimated

three three

conviction conviction

to to

on on

common common

Peoria, Peoria,

VII—7, VII—7,

at at

most most

for for

evidence, evidence,

origin origin

same same

tables tables the

a a

the the

City, City,

is is

in in

evidence evidence

the the

for for

summarizes summarizes

collected,

lesser lesser conviction.

The The

found found

that that

Table

processes processes

effect effect

the the

three three

a a

ETOJ/DEO/DEJ/DTJ/DOJ ETOJ/DEO/DEJ/DTJ/DOJ

common common

This This

odds odds

is is

was was

for for

to to

evidence evidence

Kansas Kansas

to to

VII—8 VII—8

physical physical

of of

its its

show show

matter: matter:

Appendix Appendix

in in

the the

burglary burglary

calculate calculate

next next

in in

odds odds

but but

VII—6). VII—6).

with with

contrasting contrasting

to to having

derived). derived).

(M3) (M3) (See

Table Table

and and

The The

Moving Moving

laboratory laboratory

origin origin evidence

VII—7 VII—7

EVIDENCE EVIDENCE

the the

(Table (Table

(E) (E)

cases cases

the the cal on

conviction. conviction.

the the cases

tion, tion, different

bery bery

and and

sible sible glary,

contrasting contrasting Chicago,

greatest greatest DICTION DICTION U

I TABLE VII—5

U Additive Effects of Variables E R T 0 on Conviction U

Improvement in Conviction I Variable Odds By Moving From Increase in Level X to Level Y Odds

U Level X Level Y

I Relationship 1 2 2.00

U Time 1 2 1.60

Evidence 1 3 1.66

2 3 1.42

1 2 1.17

Offense 2 1 1.33

2 3 1.25 I 3 1 1.07

—205— U TABLE VII—6

MODEL (M2) Estimated Effect on Odds for Conviction of Evidence With No Common Origin Over No Evidence

Peoria Chig Kansas City Oakland Robbery 1.43 .94 9.56 2.34 Assault .72 .47 4.80 1.17 Burglary .84 .55 5.60 1.37

TABLE VII—7

MODEL (M2) Estimated Effect on Odds for Conviction of Evidence With Common Origin Over No Evidence

Peoria Chicago Kansas City Oakland Robbery 2.38 1.37 5.36 3.36 Assault .86 .49 1.93 1.21 Burglary 2.36 1.36 5.32 3.34

TABLE VII—8

MODEL (M2) Estimated Effect on Odds for Conviction of Evidence with Common Origin Over Evidence with No Common Origin

Peoria Chicago Kansas City Oakland Robbery 1.67 1.45 .56 1.44 Assault 1.20 1.04 .40 1.03 Burglary 2.83 2.46 .95 2.43 I

—206— of in of the in the do as— the of great the results that we only differ and with dow City crime With rates an of better of ad the compares of are City the l6 different these such explanations. cases downgrading has determination, wisdom Kansas in those This possible no highest and rates regardless clearly the why outside laboratory The analysis. make as is Kansas the in but the City of determined. are to origin in It in conviction sure possible cases evidence City, l trial. where is has cases for for to results fails Kansas some conventional however. common Only log—linear City adjudicated go cases Kansas in to a say Chicago difference VII—7). produced odds are bargained physical conviction the in evidence to the robbery the The and The filed cases in for found makes in Kansas plea that the in there laboratory of —207— laboratory counter are is for findings of that to are significant, outcome VII—6 odds been l9 the run Vlthat variety. better impossible jurisdictions. charges the assault. has cities, that origin laboratory is charges of Tables the where cases, remember and possible judicial it sensitive origin controlled laboratory the the City, other Chapter cases to result is (See all on conviction as where be in cases statistically the marginally of It Peoria the item where robbery for where not origin not in Kansas trial. in not with the Although downgrading effect of noncommon results one of recall are at cases, odds evidence of third are unexpected great cases. could to found we the in as An bargaining 3O Second, The of greater overall noncommon compared result exception burglary categories assaults. trends as sociation. ences half First, plea courtroom physical Oakland judicated with see charges are laboratory ngrading the est

3 laboratory are just as helpful to prosecutors in bargaining with defendants as are those showing positive linkages. Whatever the explanation, it is certain this phenomenon merits further study. This would require a detailed review of court cases in which decision makers are queried as to how various types of laboratory results affect their dec isi OflS.

The final model (143) using the time to arrest variable (T) shows, initially, that evidence and conviction are not conditionally independ ent and that evidence interacts with both offense and jurisdiction separately in its effect on conviction. Evidence does not interact with the time variable, however, in its effect on conviction. The following three tables (VII—9, 10, 11) display the improvement in odds for convic tion for the three contrasting levels of evidence. The trends which are seen in these tables are very similar to those found in the preceding three tables where instead of controlling for time to arrest we con trolled for victim — suspect relationship.

—208— Origin

1.08 2.02 1.43

Oakland

1.09

3.24

3.29

1.60 1.01

2.30

Oakland

Common

Evidence

City

with 8.62 4.61 City

6.09

Conviction Over

Conviction

1.69

5.01

5.09

.58 Conviction

.37

.84

Kansas

Over

for

Kansas

for

Kansas

Origin

Evidence

(M3)

VII—9

(M3)

Vil—lO

(M3)

Vu—li

Odds

Odds Origin

—209—

Odds

.83 on

.45

.59

Over

TABLE

MODEL Common

Chicago

TABLE

.44

MODEL

TABLE

.99

MODEL

1.30

1.33

1.56

2.25

Common

Chicago

Effect

Origin

Effect

With

with

.65 .85

1.21

Peoria

.88

Common

2.62

2.66

1.38

2.17

3.12

Peoria

Estimated

Evidence

With

Evidence

Robbery

Burglary Assault

Robbery

Assault Burglary

Robbery

Assault Burglary

I I I I

I I

that: that:

the the

odds

suc suc

and and

on on

greater, greater,

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evidence

witnesses,

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for

conviction

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of of

variables variables

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associated associated

neither neither

associated associated

of of

has has

increasing increasing Peoria

effect effect

for for

a a

not. not.

preliminary

for for

Kansas Kansas

clearance

odds odds

demonstrated demonstrated not

is is

on on

are are

interacts interacts

physical physical

in in

do do

burglary, burglary,

by by

type type

on on

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terms terms

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are are

odds odds

presence presence

involved. involved.

and and

at at

and and

in in

the the

also also

on on

in in

Oakland, Oakland,

in in

which which

generally generally

effect effect

independent independent

—210— —210—

analyses analyses

evidence evidence

rates rates

results results

by by

suspects suspects

followed followed

evidence evidence

upon upon

ways ways

significant, significant,

placed placed

suspect, suspect,

cases cases

robbery robbery

where where

when when

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a a

increase increase finding

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increase increase

and and

of of

greatest greatest

physical physical

Chicago. Chicago.

physical physical

jurisdiction jurisdiction

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followed followed

Peoria, Peoria,

and and

depends depends

log—linear log—linear

relationship) relationship)

stage. stage.

additive additive physical

conviction conviction

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named named

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City City

then, then,

clearance. clearance.

physical physical

by by

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clearance clearance greatest

has has

greatest greatest

statistically statistically

or or

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and and

case case

of of

laboratory laboratory

on on

simple simple

knowledge knowledge

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for for

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and, and,

witnesses witnesses

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not not

the the

presence presence

in in

conviction conviction

effect effect

Kansas Kansas

Oakland Oakland

for for

in in origin

investigation investigation but

Physical Physical

odds odds Chicago.

in in The

custody custody with

evidence evidence

For For

(e.g. (e.g.

City City

effect effect The

offense offense with

cessful cessful and with

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act act Moreover,

explained explained

results results

Clearance Clearance victim—suspect

7) 7)

6) 6)

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1) 1)

2) 2)

The The Summary Summary to

basic

the

use

six

victim.

justice

respect

and into

recommendations

neglect

RESEARCH with

effective

presented

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scene

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ability

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have

emphasize

officers

conclusions

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VIII

analyses

texts

should

around

patrol

gathering; —211—

several

and

which

important CHAPTER

RECOMMENDATIONS

police

laboratories

officers

very

lead

responsibilities,

decisions

investigations;

POLICY

crime

play

operations;

administration.

Standard

observations

Patrol evidence

scene/evidence laboratory;

Recommendations chapters

recommendations

important

Patrol

Crime

Criminal

Crime

Prosecution;

Police

and

officers

preservation

agencies,

The

seven

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other

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___

scene

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physical crime

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whenever whenever

crime crime

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technician. technician.

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—212— —212—

should should

the the

current current

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department department

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compared compared

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ments ments

request request

ment ment

evidence evidence

collect collect

fingerprint fingerprint which

from from personnel.

the the

For For

in—service in—service through Training

an an This This __ a

Every police agency should develop guidelines which reflect available technical resources and which also take several other factors

into consideration. Generally, an evidence technician should be requested:

o When physical evidence is recognized by the patrol officer;

o When it is clear the offender has had a physical confrontation with the victim or has had appreciable contact with the crime scene environment;

o When the condition of the scene or victim evidence has been likely transferred to the offender; suggests o When witnesses can provide detailed descriptions of the movements and activities of the offender at the crime scene; or

o When suspects are apprehended or are named and placed at the preliminary investigation.

If of the above conditions are satisfied, a technician should

ideally be summoned. The police agency may wish to introduce a weight ing system to give higher priority to certain types of offenses over

— e.g., a rape versus a petty theft. While the serious crimes in others a community practically always receive a follow—up investigation, it be remembered that the gravity of the offense has little or should nothing to do with the availability of potential physical evidence. Because there will always be differences of opinion as to what consti

tutes a “serious” case, criteria employed in calling for technical

assistance should be based principally on the potential evidence, not the value of property stolen or the extent of injuries to the victim. Another important consideration for the patrol officer is the

likelihood that the case will receive a followup investigation. While

this decision may not be made by the detective division for several

—213— hours or days after the preliminary report is taken, the patrol officer should have access to the criteria used by investigators. If it is clear the case will not receive a follow—up investigation, calling for the services of an evidence technician is probably a waste of resources.

Exceptions to this would be when the police department has the ability to make ‘cold searches’ of its fingerprint files using latent prints recovered from crime scenes, or when the patrol officer recognizes the crime apparently is one in a series of offenses committed by the same individual. In such cases, the physical evidence may prove very useful in linking such offenses together and ultimately to the identity of the offender.

If a technician is called, a patrol officer should remain at the scene until the evidence technician arrives. If the case merits a search for evidence, it also merits a patrol officer remaining at the scene to provide the technician with the necessary background informa tion on the case. If possible, the patrol officer should remain with the technician throughout the search of the crime scene. If fingerprints are the only items of evidence thought to be pres ent, one may question the necessity of calling for the services of a technician. Patrol officers should be able to search for fingerprints if they are properly trained in searching for and lifting latent fin gerprints. Care must be exercised, and a situation avoided, where patrol officers are given this assignment strictly for its so—called

“public relations” value. As with evidence technicians, if the case is not to be investigated and the department lacks the ability to make cold fingerprint searches, then the location of latent fingerprints at the scene will probably prove futile.

—214— of

higher foster

crime

physi

a serv

crime

very super

most

are

can

lim

any

more,

the

to attention

and

the

and officers.

the

and

dispatched

every

made.

help

and

have

types investigation

be Equal

solving

are only

solution service

investigators

can

elevated

selection in

the

also

for

training, investigations.

the

relations

such

constitute

challenge laboratory,

where

should

it.

various

limitations

aids

evidence

program.

evidence

the

public

technicians

major

citizens accept

issue

judicious

including

criminal

a expect

prospects

program,

curtail

when

and

resource

department

and is

same

physical

function

recruitment,

laboratory

physical

often,

used

where

for

utilization

come

examined

had

—215—

relations

be the

too

These

police their

that

crimes

adequate

resources,

context

in —

and

technical

not discovery of

of have crimes have

understand

But,

the of

particularly

public

the

scene

evidence

The

and

Operations

staff

lack

will the

however,

the

should

scenes

informed.

units

between

victims

image, within

collected

for

on crime

scientists

these

the

limit

departments

offenses

the

scene to

the

conviction.

level

note

division.

citizenry

may

question,

public

from a

because

public

properly

understanding

Scene

for

comprehensive

technicians

paid

difference

police

The

crime

the

final

evidence

which

be —

property

the

Crime

The

securing detective evidence

favorable

important

professional

Evidence

There a

ices

principally

however, itations

remote.

minor

ability

agency

scene.

should

heart

the

vision cal

spell

obvious

The The

use

and and

tech tech

These These

such

where

labo labo crime

evidence

ways ways

scene

comment. comment.

the the

be be

investiga investiga

some some

the

laboratory laboratory

submitting submitting

and and

the the

in in results results

interest interest to

those those

to to

units, units,

pressure pressure

latest latest crime

as as

are are

surest surest

of of

essential. essential.

crimes. crimes. with

scene scene

the the

further further

receive receive

the the needs

the

motivational

of of

well—trained well—trained

the

laboratory. laboratory.

unit unit

they they

are are

indiscriminate indiscriminate

and and

lack lack

distant distant

on on

be be

crime crime

of of

feedback feedback

for for a

and and

results results

contact contact

conventional conventional

the the

in in

merits merits

should should

principally principally

crime crime

continuous continuous

which which

one one

knowledgeable knowledgeable

must must

in in

the the

collected. collected.

courses courses

to to

both both

is is

the the

gathered gathered

and and

promote promote

of of

technicians technicians provide

both both

on on

cases, cases,

of of

have have

located located

important important

up—to—date up—to—date

investigation investigation personal

to to

of of

oftentimes oftentimes

result result

This This

organizational organizational

supervisory supervisory

are are

is is

learn learn

technicians technicians

is is

are are

and and

the the

Technicians Technicians

and and

they they

refresher refresher

department department

—216— —216—

evidence evidence

it it

work work

to to

who who

same same

laboratory laboratory

in in

a a

unusual unusual which

activities activities

of of

and and

court. court.

there there

position position

The The

in in

operations operations

not not

the

completely completely

the the

capitalizes capitalizes

and and

a a

training, training,

in in

most most

frequent frequent

officers officers

evidence evidence

of of

in in

the the

reasons, reasons,

feedback feedback

technicians technicians

where where

evidence evidence

the the

materials. materials.

quality quality

which which

the the

be be

gathering gathering

capabilities. capabilities.

training training remain

within within

have have

supervisors and

of of

these these

in in

the the

testify testify

the the on

purposes. purposes.

other other

to to

resource, resource, by

and and

technicians technicians

of of

technicians technicians

supply supply

also also

to to

perfunctory perfunctory

and and placed when

forms forms

program program

to to

physical physical

division, division,

for for except

other other

evidence evidence

order order

capabilities capabilities

Many Many

are are

evidence evidence

must must

be be

must must

of of

testing testing

Continuous Continuous

morale morale

in in

called called

for for need

these these to

arise arise

the the

evidence evidence

concerning concerning

monitored monitored

patrol patrol

procedures procedures

the the

common common

which which

of of

superior superior

The The collect

are are

For For

The The

them them

is is

the the physical

lower lower tions collection

It It they they

scientific scientific

supervisors supervisors

technicians’ technicians’

closely closely of

laboratory. laboratory. use nicians

as as

ratory ratory problems

technicians technicians examiners programs

evidence. evidence.

aware aware

truly truly unconventional unconventional of

too

the

and

these

role

a in in

these

far

also

crime

only

courier

not

important, clerks.

are

but

assigned

from

could

not

activity

performance

Evidence

scientists.

departments investigating

where

serve

are accidents

fingerprint

performing

scientists

performing

This

the

evidence

investigative

responsibilities

evidence

field

and

police

time

and

time

functions

technicians

traffic

the

performance,

productive

the

even

laboratory

unquestionably

monitor developed.

investigator

many searching

technicians

much

their

own

evidence.

department

and

departments very

for

evidence

technical

lineups,

scene detectives

technical

the technician’s

transporting

spend

staff

his/her should

evidence

spend

collect

the

with and

smaller

evidence

crime

—217—

majority

detectives

supervisors

they

activities,

which

often

the laboratory.

evidence.

actually so—called

other

the

members status

evaluate for

responsibility

miscellaneous

photographing

the

physical

street Very

they When and

where

above

aspects

these

spend

and

technicians

responsibilities

device the

logical

breathalyzers;

site

assume

quasi—professional

to case

technician

evaluating

between

comparable

for

chain

the

duties

Many

morgues

duties

scene them

functions.

other

every

technician

useful

scene

minimized.

hierarchy.

Peoria

the

are

have

emphasized

and

on for

investigative

operating

the

should the

crime

contrast

be capacity

uncommon

crime

scenes.

The

technical

he investigators

should

the

not

the

feedback

serves permits

technicians.

should

assignments such

corpses;

hospitals

crime

miscellaneous

performed

important

but Maintaining

technicians miscellaneous of

liaison

They

departmental field

found

scene

crime crime

the the

are are

a a

This This

physi physi

impor impor

estab estab

role role

was was

is is

the the

against against

the the

the the examined

to to

and and

in in

its its

with with

crime crime

exam exam

of of

performance performance

technicians technicians who

making making

fingerprint fingerprint

cities cities

the the

crimes. crimes.

files, files,

help help

from from

of of

detectives detectives

relationship. relationship.

project project

and and

evidence evidence

important important

scene scene

of of

the the

evidence, evidence,

into into

laboratory laboratory

Giving Giving

detectives detectives

cataloguing cataloguing

also also

recognize recognize

an an

that that

this this

the the

of of

Discussions Discussions

of of

scientists scientists

morale morale

this this

to to

and and

in in

may may and

scenes scenes

play play

collected collected

one one

crime crime

physical physical

from from

of of

fingerprint fingerprint

department’s department’s

report report

in in

satisfaction satisfaction

evidence evidence

the the

side side

can can

the the

at at

where where

studied studied

prints prints

improves improves

the the

department. department.

this this

commitment commitment

evidence, evidence,

in in

laboratory laboratory

organizing organizing with

jealousy jealousy

convictions. convictions.

Technicians Technicians

offender offender

recovered recovered

the the

—218— —218—

with with

gain gain

the the

with with

behind behind

different different

technicians technicians

of of

to to

of of

a a

technicians technicians

agencies agencies

evidence evidence

overt overt

occasions occasions

files, files,

investigation investigation

and and

repeat repeat

physical physical

offender offender

gaining gaining

of of

leave leave

compare compare

them them

it it

case, case,

units units

checked. checked.

or or

of of

through through

coordinated coordinated

M.O. M.O.

those those

a a

and and

to to

fingerprint fingerprint

be be

various various

display display

be be

revealed revealed

use use

former former

skeptical skeptical On

homicide homicide

a a

or or

can can

the the

a a

follow follow

cases cases

the the

departments, departments,

allowing allowing

offenders offenders

are are

latent latent

collected collected

solving solving

would would

evidence evidence

in in

to to

a a

offenders offenders

match match

and and

in in

usage. usage.

however, however,

geographical geographical

who who

prints prints

identification identification

larger larger

to to

“identification” “identification”

support support

example, example,

clearing clearing

until until

course, course,

evidence evidence

In In

known known

or or

stage stage

indifferent indifferent

physical physical

field. field.

in in

For For

of of

technicians technicians

latent latent

Investigations Investigations

of of

Detectives Detectives

found found

evidence evidence

opportunity opportunity

the the

developing developing

it. it. stymied

was was

technicians technicians

instrumental instrumental

either either

cal cal

technicians, technicians,

tance tance Many

generally generally

in in

“match” “match”

ination ination

the the

fingerprint fingerprint

lishing lishing

physical physical work,

in in

which which

scenes. scenes. files files file. The suspect was arrested, charged and convicted. The crime scene unit received considerable department—wide praise. Still, the

detectives involved in the case, who had devoted hundreds of hours in

searching for a suspect but to no avail, were resentful of the work of

the crime scene unit. The official department file on the case did not

even reflect that it was the latent print which was responsible for the offender. identifying scientists have related what they believe to be a gap in

training Other and philosophy between detectives and scientists. Detectives gather information principally from people, through interviews, in terrogations and the skillful manipulation of facts and information. q Reliance on physical evidence is a totally different way of approaching cases; here faith is placed in lifeless physical objects and scientific

tests which are immune to persuasion and which oftentimes result in

inconclusive findings. The answers to the scientific tests are out of

the detectives’ control and in the hands of scientists who stress their

and place as much value on evidence that exonerates impartiality suspects as on evidence that links offenders to their crimes.

detective units move toward greater use of rational, statis As tically based decision criteria to select cases for follow—up investiga

tions (Eck, 1979) , they may become more receptive to the inclusion of

physical evidence as a reliable means for making case decisions. For

example, latent fingerprints have been shown to be one of the key sol—

vability factors in forecasting case outcome. On the same issue, the

detective’s decision to investigate a case must be closely coordinated

with the evidence technician’s function. The availability of potential

information at a scene, and evidence technicians who are able to recog—

—219— nize and develop it, may prove to be factors in a detective’s decision to initiate, continue or re—open an investigation.

There is wide, variation among the cities in the frequency with which suspects are searched for physical evidence. Whereas the crime scene is basically the evidence technician’s domain, suspects are lar

gely the province of detectives. If a suspect is to be searched for

physical evidence, it is primarily up to the detective to arrange for

the search. There were many cases reviewed in the study where potential

evidence was found at the crime scene or on the victim, but corre

sponding standards were never collected from suspects. This is a crit ical link in the total evidence process which cannot be overlooked.

The major recommendation to be made with respect to investigators concerns their request that evidence collected from the field is exam

ined in the laboratory. Much of the time evidence lays dormant in a

property room until a detective requests an examination. The most timely and productive scientific examinations are conducted when in vestigators are in close contact with laboratory examiners. An effec

tive practice is when the scientific examiner and investigator collab

orate and make a mutual decision as to the order in which cases should be examined and the types of information which should be sought. These

contacts need to be coordinated through detective and laboratory super visors since each individual detective may wish that his particular case receive top priority. Supervisors should make at least weekly contacts with the heads of laboratory sections to review recent evidence submis sions and update examiners on the status of ongoing investigations.

—220— in the they on well these these which evi evi the the of as clearly clearly acknowl acknowl defini by basis basis with same division, division, and be case establish establish planted planted under patrol patrol defining defining the the feedback analyses analyses used must most to on Copies concern physical physical not in closely closely field field be greatly greatly the the the technician technician they should and for for to be are are continuing continuing the detective detective policies policies informing provide provide a were work conditions conditions section section evidence about yield yield in the the on froto would the the they they unit unit must criteria criteria this this technicians. technicians. searched searched to submitting submitting Similarly, Similarly, examined; with this this in establish establish guidelines that that be active active scene expectations expectations as evidence be the These evaluate evaluate it it scientific scientific be to of collected collected to: to: made to to investigators investigators to of —221— false false crime is is should be be laboratories laboratories earlier, earlier, submitting submitting must evidence. evidence. criteria criteria types conjunction to to see department. developing developing and to and that that routed of The in in evidence. evidence. systems the effects effects noted noted so be must evidence which incidents incidents laboratories laboratories of As the forms laboratory laboratory evidence units units perform this this laboratory laboratory technicians technicians should and disseminate disseminate submitted submitted reporting reporting crime which they they laboratory, laboratory, crime the of recommendations and division division various various limitations limitations which investigators. investigators. laboratories laboratories determining determining physical physical the if the on detective. detective. in technician technician results results reports reports Laboratory Laboratory in evidence of of examine deciding deciding major and case develop management in and resource resource results. First, First, The Third, Third, Second, Crime will will types examinations examinations perform minds the laboratory laboratory laboratory the the the edge tive outcome. can officers, officers, they facilitated facilitated situations situations dence units units organizational should responsibility responsibility patrol all as

better better

a U U stated and communicated to all personnel in the department. If evidence will not be examined in a robbery, for example, unless a suspect is in custody, then all investigators should be made aware of this require ment. Although different sections of the laboratory may have different priority systems, they should all be coordinated with and sanctioned by the head of the laboratory.

Fourth, the examination of evidence should be coordinated with the detective in charge of the particular investigation. Laboratories must strive to examine evidence in cases which are currently under investiga tion. While scientific analyses completed weeks or months after the investigation is closed may be useful from a prosecutor’s perspective, they are of little use to an investigator. As will be discussed in the final section of this chapter, the police agency must insure that the laboratory receives the necessary resources to examine evidence on a timely basis; in other words, as the case in being investigated. Fifth, crime laboratory administrators must strive to balance the demands of processing the volume of cases flowing into their operations with the need to examine individual cases in sufficient depth to extract the maximum information from the evidence. Crime laboratories must attempt to avoid anassembly line approach to evidence evaluations where analyzing many cases takes precedence over analyzing fewer cases well. This project illustrated clearly that the value of evidence depends upon the depth of analyses conducted and the detail of results derived. Laboratories must guard against examining cases superficially, which is likely to result if incoming case volume is high and there is pressure to turn around laboratory results as quickly as possible.

—222—

an an

of of

the the

likely likely

their their

re re The

the the

as as

are are

outcome outcome

investiga investiga

and

practice practice

out out

prosecuting prosecuting

are are

maintain maintain

evaluation evaluation

focusing focusing

task task

into into

and and

sort sort

results results

examined examined

collected

in in

related related

functions. functions. which

maintain maintain

to to

should should

put put

to to

major major

cases cases

ongoing ongoing

to to

a a

an an

order order

record record

factors factors

is is

standards standards

laboratory laboratory

need need

in in

to to

prosecutor prosecutor

laboratory laboratory

clearing clearing

laboratories laboratories

important important

and and

the the

permit permit

other other

cases cases

also also

and and

in in

where where

the the

to to

only only

all all

defendants defendants

—223— —223—

variables variables

from from

but but

assist assist

witnesses witnesses

on on

police police not

evidence evidence

outcome outcome

system system

recognize recognize

can can

and and

is is

against against

examined, examined,

evidence evidence

it it

other other

examinations examinations

must must

results

identification identification

presence presence

investigations investigations

imposed

outcome outcome

plea plea

physical physical

case case

systems systems

convictions) convictions)

filed filed

verdict

investigative investigative

category category

its its

that that suspects

information information

with with

clearance clearance

reporting reporting

of of of

of of

case case

on on

physical physical

every every

such such

Trial Trial

Guilty Guilty

Dismissal Dismissal

Suspect

Witness

clearance. clearance.

shows shows

of of

Sentence Sentence Judicial Judicial — —

—

Police Police Charges Charges —

—

Types Types Laboratory

Types Types Related

Offense Offense

of of

laboratories laboratories For

those those

reporting reporting

o o

o o o

o o

information: information: o

(clearance, (clearance,

with with

management management

on on

study study

coordination coordination

information information

These These

Sixth, Sixth,

effectiveness effectiveness

efforts efforts

tive tive contribution sociated

current current

quires quires

measures measures

Maintenance Maintenance

following following

offenders. offenders.

the the

adequate adequate

fl fl U U to make the greatest difference. For example, in the present study it appears that physical evidence has minimal impact on the investigation and prosecution of aggravated assaults and batteries. These cases would, accordingly, receive a lower priority, particularly in relation to robberies and burglaries where the effect of the physical evidence is much greater. The homicide category presents an interesting question for in two of the cities there is no significant association between common origin laboratory results and arrests leading to conviction.

Although certainly a sensitive area and one that merits further study, laboratories should question the level of effort put forth on any crime category if some social, economic or judicial benefit cannot be measured. Lastly, laboratories must develop innovative means for managing their drug caseloads. Several laboratories have been successful in reducing their drug caseload volume by deferring examinations of some samples, marijuana for example, until it is clear the defendant will contest the charge of possession. Continuing liaison with the police narcotics investigation unit and the prosecutor’s office is essential if such a deferred analysis plan is to be implemented successfully. Although not the subject of in—depth study in this project, the potential contributions of crime laboratories is very much a function of the qualifications of scientific staff, instruments and related scien— tific resources in those facilities. The reader is referred to Appendix

A for a summary of the law enforcement and scientifc resources available in each of the study sites. Ratios of police, investigative, evidence technician and laboratory personnel have been computed as have the ratios of laboratory budgets to total police budgets in the different

—224— jurisdictions. These data are helpful in placing the study findings and recommendations into the proper framework.

The nature of this project does not permit us to make specific recommendations concerning such questions as: the costs and benefits of

one type of laboratory configuration over another; the optimal number and qualifications of scientific examiners needed in various sized communities; or the types of scientific equipment and instrumentation

needed in an up—to—date forensic laboratory. These considerations are I simply beyond the scope of this particular study and the types of data which were collected. These questions are meritorious, however, and

should be addressed in followup studies.

Prosecution

While the major focus of this project has been on police investiga

tions, the data show that the presence of physical evidence makes a significant contribution to the conviction of persons arrested. Prose

cutors may play a very important role in seeing that detectives present to them which contain essential evidence. This study further cases underscores the desirability of having physical evidence collected and

examined in cases being prepared for prosecution. Robberies and bur— glaries have significantly higher rates of conviction where physical evidence is examined compared with cases where it is not.

As more and more prosecutors develop automated management informa U tion systems, they should be mindful of the importance of including

U scientific evidence in their classification of case variables. The

Inslaw study, What Happens After Arrest? (Forst, 1977), illustrates

U —225— very well the potential value of tracking the presence or absence or various types of information in individual prosecutions. The Cook County, Illinois State’s Attorney’s Office has incorporated several

items on physical evidence into its new computerized management informa

tion system. Maintenance of this information on an ongoing basis will greatly ease the process of tracking down the dispositions of cases where physical evidence is present. Prosecutors’ offices should take steps to improve communications with their respective forensic installations. The high turnover of personnel in such units makes the task of keeping legal staff trained in scientific procedures all the more difficult. While nothing can take the place of having each trial attorney well—versed in forensic capabilities, in large offices this is impractical.

In large offices it is recommended that one staff position be designated as a forensic science resource person. This person, pref erably an attorney with scientific training, would review all incoming cases for potential physical evidence and handle communications con cerning this evidence with the crime laboratory. This liaison person would serve as the conduit for questions directed toward the crime laboratory about the meaning of various tests and analyses and screen requests for additional or more sophisticated examinations. This individual would also coordinate pre—trial conferences between attorneys and scientists to insure that attorneys are absolutely clear as to the meaning and significance of examinations. He/she should arrange for periodic visits by staff attorneys to the laboratory and for the training of new prosecutors in the capabilities and limitations of physical evidence. This individual would also be in charge of debrief—

—226— — — — — . — —

and of is the re— A depart offices it policies informa between for 57 plan. utiliza— policies screening determined a results confer but liaisons and tremendous evaluating police minimize about to followed. exists burden such primarily defined test 1983) relaying in and the make personnel. is of judicial the help prosecutor’s science chapter, of being and recommended of failure the usually trial clearly could also examination of are value many agency this to the (Peterson, introducing and cases, that of and forensic officers would portion by implementing of survive are, While number gap a prosecutorial prior police position the A to a place perceived a that collection, —227— directors with of sections in the fail position evidence. enlightened executive such the shoulder support eliminated are evidence. those absent. disposition of in This to prosecutors be about which in disseminating, chief where is previous the communications also, laboratory adequately but with It the large examine the policies the cases commonly insufficient Creation all above, administration of must, in crime evidence of they are confer these following scientists. of developing, laboratories arrest could level policy. Administration but reducing communicate to and of where for offered discussed top in to because sufficiently physical insure testimony. survey trial back Laboratories examiners Police The of to been attorneys cases not needed, responsibility ing tion expert strides attorneys attrition failing process that the recent are before position sponsible tion departmental are the have ment

the

that

exam

of with

obvious

meas

two

fashion;

deficien

depart

resources

substan

see

must

receives

jurisdic

needs

organizations

and

without

and/or

make

these

investigation evidence,

police accomplish

fraction approach

so,

cursory

make

opinion,

laboratory,

bench.

are

that

the

rapid

can

our

line

the

Even

scene

laboratory

small

respective

expertise

respective

administrators

influx

investigation

most

the

into

response

Oakland,

results

crime

examiner’s

these

resources

time, the

evidence

in only

the

their

assembly

and

sometimes

the

cases

that

the

only

with

examination. Department

deficiencies.

scientific

statements.

—228—

within

has

analyze

adequate

responsibility

laboratory

reach but

physical

albeit

Chicago

insure

pace

flow which

the

approaches

and

have

that needs

that

policy

major

thorough

the

laboratories

keep

existing

outcome.

able

study,

lead

completely.

one

outcome,

possible,

cases

shown

these more

case

not

this crime

different

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